<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:f5130a22-9291-465c-89a0-d05126cdb173,g:e23653f4-f428-4e06-bd5a-099ebf03abac-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.swgas.com/role/Cover" xlink:type="simple" xlink:href="swx-20220630.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/Cover" xlink:type="extended" id="ibedb7811db264e81b295ec82620f0a45_Cover">
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_19930fbb-9c1e-40fd-8b76-716b50f7d1e6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_DocumentType_19930fbb-9c1e-40fd-8b76-716b50f7d1e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_741774a8-1e01-48f0-be75-a26f6669ae07" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_DocumentQuarterlyReport_741774a8-1e01-48f0-be75-a26f6669ae07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_55156b01-a98e-489b-84c7-6fae54fce77b" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_DocumentPeriodEndDate_55156b01-a98e-489b-84c7-6fae54fce77b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_3a4dc7e0-2486-46b3-8930-9c4aa8b9a0e0" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_DocumentTransitionReport_3a4dc7e0-2486-46b3-8930-9c4aa8b9a0e0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_f920fd43-ad4c-4696-8a1c-b7ff36a560aa" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityFileNumber_f920fd43-ad4c-4696-8a1c-b7ff36a560aa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_c61edf7a-31ac-4ede-a44a-307b155dd364" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityRegistrantName_c61edf7a-31ac-4ede-a44a-307b155dd364" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_c41707e5-14ca-4b21-8c91-9d6fc3c9233a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityIncorporationStateCountryCode_c41707e5-14ca-4b21-8c91-9d6fc3c9233a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_079892f0-1390-42e7-bf9b-45c563e9c254" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityTaxIdentificationNumber_079892f0-1390-42e7-bf9b-45c563e9c254" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_b2dd8a8a-8dea-4e2d-814d-d638de0ea28c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityAddressAddressLine1_b2dd8a8a-8dea-4e2d-814d-d638de0ea28c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine2_745af8d4-860d-40ee-b3a5-5400d4fd950d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressAddressLine2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityAddressAddressLine2_745af8d4-860d-40ee-b3a5-5400d4fd950d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_65a2f702-1dd5-41ab-a61a-8323efe62f4a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityAddressCityOrTown_65a2f702-1dd5-41ab-a61a-8323efe62f4a" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_b0e7df88-a2db-4438-afbf-920b3c83af4b" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityAddressStateOrProvince_b0e7df88-a2db-4438-afbf-920b3c83af4b" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_1d797438-e992-402d-a298-9eda944306de" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityAddressPostalZipCode_1d797438-e992-402d-a298-9eda944306de" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_42a27f07-e053-40d5-b82a-89f6cebe279f" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_CityAreaCode_42a27f07-e053-40d5-b82a-89f6cebe279f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_2fd1493e-ae8c-4424-94f6-b9ba22cbd98d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_LocalPhoneNumber_2fd1493e-ae8c-4424-94f6-b9ba22cbd98d" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_d21577ba-61e2-4e26-bfc2-66cbbf5ad076" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_Security12bTitle_d21577ba-61e2-4e26-bfc2-66cbbf5ad076" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_d2d87e41-359c-4bfc-945b-954a4f187503" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_TradingSymbol_d2d87e41-359c-4bfc-945b-954a4f187503" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_53f499f6-f9cb-47bc-a110-fae0c037795f" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_SecurityExchangeName_53f499f6-f9cb-47bc-a110-fae0c037795f" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_219c2bfb-b61a-4117-9d94-4493e0fd9e62" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityCurrentReportingStatus_219c2bfb-b61a-4117-9d94-4493e0fd9e62" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_ad6ab777-4db0-4b75-ad99-b8a6898a9f5e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityInteractiveDataCurrent_ad6ab777-4db0-4b75-ad99-b8a6898a9f5e" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_f8c4e77d-3bb2-4031-867f-5b18e9624eb5" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityFilerCategory_f8c4e77d-3bb2-4031-867f-5b18e9624eb5" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_49835361-f8db-405b-b240-93149d6bccd5" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntitySmallBusiness_49835361-f8db-405b-b240-93149d6bccd5" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_e920a968-ea13-4488-a64c-36aeb6fb85b1" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityEmergingGrowthCompany_e920a968-ea13-4488-a64c-36aeb6fb85b1" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_6c4816e6-3bd7-4fec-aec1-fe2edf62efc6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityShellCompany_6c4816e6-3bd7-4fec-aec1-fe2edf62efc6" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_f7842ddd-3719-42df-a8ce-be69920344e6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_f7842ddd-3719-42df-a8ce-be69920344e6" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_5fa353ad-688e-442c-b5e8-338395721602" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntityCentralIndexKey_5fa353ad-688e-442c-b5e8-338395721602" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_24f58b62-b0a8-4874-b65a-cac4b6be7826" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_DocumentFiscalYearFocus_24f58b62-b0a8-4874-b65a-cac4b6be7826" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_267d16ca-cd7d-4787-957d-ba53444c2b3a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_DocumentFiscalPeriodFocus_267d16ca-cd7d-4787-957d-ba53444c2b3a" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_d47855cf-d783-49b0-83b4-93f4576ecf33" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_AmendmentFlag_d47855cf-d783-49b0-83b4-93f4576ecf33" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_NoTradingSymbolFlag_f522aec8-391e-4652-ad20-7f2d67a1fb15" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_NoTradingSymbolFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_NoTradingSymbolFlag_f522aec8-391e-4652-ad20-7f2d67a1fb15" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_3d43cc30-5176-40e4-8ab2-6a99878b7100" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_CurrentFiscalYearEndDate_3d43cc30-5176-40e4-8ab2-6a99878b7100" xlink:type="arc" order="30"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitiesTable_045fcdde-6fb9-4d30-8bb9-1bcee3dbdb25" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_EntityInformationLineItems_0ab841d5-33e2-4548-b678-2bd1bae3a757" xlink:to="loc_dei_EntitiesTable_045fcdde-6fb9-4d30-8bb9-1bcee3dbdb25" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_5ca8ba4a-c328-4518-9aca-12dbea8886e7" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_045fcdde-6fb9-4d30-8bb9-1bcee3dbdb25" xlink:to="loc_dei_LegalEntityAxis_5ca8ba4a-c328-4518-9aca-12dbea8886e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_5ca8ba4a-c328-4518-9aca-12dbea8886e7_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_5ca8ba4a-c328-4518-9aca-12dbea8886e7" xlink:to="loc_dei_EntityDomain_5ca8ba4a-c328-4518-9aca-12dbea8886e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_dcdcc5b4-c860-44c9-9f73-78f70d2050b1" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_5ca8ba4a-c328-4518-9aca-12dbea8886e7" xlink:to="loc_dei_EntityDomain_dcdcc5b4-c860-44c9-9f73-78f70d2050b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_dc5e6af4-846f-42b0-a770-3ec397c5c931" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_dcdcc5b4-c860-44c9-9f73-78f70d2050b1" xlink:to="loc_swx_SouthwestGasCorporationMember_dc5e6af4-846f-42b0-a770-3ec397c5c931" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_11ca25d7-bb2e-45e7-8d18-141f2ee59edf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_EntitiesTable_045fcdde-6fb9-4d30-8bb9-1bcee3dbdb25" xlink:to="loc_us-gaap_StatementClassOfStockAxis_11ca25d7-bb2e-45e7-8d18-141f2ee59edf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_11ca25d7-bb2e-45e7-8d18-141f2ee59edf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_11ca25d7-bb2e-45e7-8d18-141f2ee59edf" xlink:to="loc_us-gaap_ClassOfStockDomain_11ca25d7-bb2e-45e7-8d18-141f2ee59edf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_8dc3abe2-3848-453d-9827-a31648ae4879" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_11ca25d7-bb2e-45e7-8d18-141f2ee59edf" xlink:to="loc_us-gaap_ClassOfStockDomain_8dc3abe2-3848-453d-9827-a31648ae4879" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_4c01422c-59b7-43a6-9333-bf8fa6378000" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8dc3abe2-3848-453d-9827-a31648ae4879" xlink:to="loc_us-gaap_CommonStockMember_4c01422c-59b7-43a6-9333-bf8fa6378000" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_PreferredStockPurchaseRightsMember_38dba2c7-5db7-432f-adae-c51714e63f32" xlink:href="swx-20220630.xsd#swx_PreferredStockPurchaseRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8dc3abe2-3848-453d-9827-a31648ae4879" xlink:to="loc_swx_PreferredStockPurchaseRightsMember_38dba2c7-5db7-432f-adae-c51714e63f32" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITY" xlink:type="simple" xlink:href="swx-20220630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITY"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITY" xlink:type="extended" id="i312502a24f8446a0931dc77a3ff2019e_CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITY">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_9fab1593-9f7d-4809-be21-a3049a31a919" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9fab1593-9f7d-4809-be21-a3049a31a919" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_db591cd3-a018-4bc0-b363-6a7e926db5f2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_db591cd3-a018-4bc0-b363-6a7e926db5f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_2f08ab0c-4f8f-4220-b82a-499bd2a44cd2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_2f08ab0c-4f8f-4220-b82a-499bd2a44cd2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_0cbccbd9-b53e-49af-8749-fb4e997e1f3a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_0cbccbd9-b53e-49af-8749-fb4e997e1f3a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_52e04f8e-8add-4656-ae6b-2adf6d362e7c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_52e04f8e-8add-4656-ae6b-2adf6d362e7c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxPortionAttributableToParent_bfe4b6ba-af5a-4442-8028-53512a9dc991" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentBeforeTaxPortionAttributableToParent_bfe4b6ba-af5a-4442-8028-53512a9dc991" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTaxOther_9f842d1e-290c-470a-a551-0e70be316daf" xlink:href="swx-20220630.xsd#swx_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTaxOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_swx_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTaxOther_9f842d1e-290c-470a-a551-0e70be316daf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_36d44ac2-2856-43d8-90da-010889360a3d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_36d44ac2-2856-43d8-90da-010889360a3d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_d00a2597-40fb-4d92-8f98-d8fe65b95d90" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_d00a2597-40fb-4d92-8f98-d8fe65b95d90" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStock_84b411cd-de1f-4015-8cdc-1151bea8d56d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_DividendsCommonStock_84b411cd-de1f-4015-8cdc-1151bea8d56d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestChangeInRedemptionValue_da182d85-0191-4ed9-8d7f-53a48363f13f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestChangeInRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bed3003a-a391-42f8-aaa5-ed0f0580a388" xlink:to="loc_us-gaap_MinorityInterestChangeInRedemptionValue_da182d85-0191-4ed9-8d7f-53a48363f13f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_98aff204-774e-4842-bfb0-7346c40425fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_b69a1c40-f653-4e88-9292-5d5c227ac6c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_036b2e37-f48d-4797-8ac0-9f31ac8f84e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9fab1593-9f7d-4809-be21-a3049a31a919" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_036b2e37-f48d-4797-8ac0-9f31ac8f84e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_f07877b2-32ab-4194-9eba-21f1814efb3c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_9fab1593-9f7d-4809-be21-a3049a31a919" xlink:to="loc_us-gaap_StatementTable_f07877b2-32ab-4194-9eba-21f1814efb3c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_9e9152a5-c923-455c-a687-eab72c821376" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f07877b2-32ab-4194-9eba-21f1814efb3c" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_9e9152a5-c923-455c-a687-eab72c821376" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9e9152a5-c923-455c-a687-eab72c821376_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9e9152a5-c923-455c-a687-eab72c821376" xlink:to="loc_us-gaap_EquityComponentDomain_9e9152a5-c923-455c-a687-eab72c821376_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_e16cb878-6ed2-4ff2-aed6-dcc009233f6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9e9152a5-c923-455c-a687-eab72c821376" xlink:to="loc_us-gaap_EquityComponentDomain_e16cb878-6ed2-4ff2-aed6-dcc009233f6a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_a8fbafd9-bf5b-462e-82bb-899bf9ada398" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e16cb878-6ed2-4ff2-aed6-dcc009233f6a" xlink:to="loc_us-gaap_CommonStockMember_a8fbafd9-bf5b-462e-82bb-899bf9ada398" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_8cfa2778-1c5b-4e8d-aab0-07c267a42ddc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e16cb878-6ed2-4ff2-aed6-dcc009233f6a" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_8cfa2778-1c5b-4e8d-aab0-07c267a42ddc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_a35bdb00-d0e2-45da-b885-f0b9f8c97859" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e16cb878-6ed2-4ff2-aed6-dcc009233f6a" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_a35bdb00-d0e2-45da-b885-f0b9f8c97859" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_ec770f88-55a9-4a17-b72b-6cf495a7f182" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e16cb878-6ed2-4ff2-aed6-dcc009233f6a" xlink:to="loc_us-gaap_RetainedEarningsMember_ec770f88-55a9-4a17-b72b-6cf495a7f182" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ParentMember_7747c84a-3529-4c55-a6e7-d132e43bbf0a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_e16cb878-6ed2-4ff2-aed6-dcc009233f6a" xlink:to="loc_us-gaap_ParentMember_7747c84a-3529-4c55-a6e7-d132e43bbf0a" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSSouthwest" xlink:type="simple" xlink:href="swx-20220630.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSSouthwest"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSSouthwest" xlink:type="extended" id="id5e0b8f440ec44a5b1494af6c1cd02ac_CONDENSEDCONSOLIDATEDBALANCESHEETSSouthwest">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_7d0bb9e4-c2ca-45ce-b73e-635a846a2008" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7d0bb9e4-c2ca-45ce-b73e-635a846a2008" xlink:to="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_PublicUtilitiesPropertyPlantandEquipmentGasPlant_0cb15308-1820-45a3-ab38-1c3c4a893a43" xlink:href="swx-20220630.xsd#swx_PublicUtilitiesPropertyPlantandEquipmentGasPlant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:to="loc_swx_PublicUtilitiesPropertyPlantandEquipmentGasPlant_0cb15308-1820-45a3-ab38-1c3c4a893a43" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation_1abb20a8-87ff-4efc-aab6-fd91db2446ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentAccumulatedDepreciation_1abb20a8-87ff-4efc-aab6-fd91db2446ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress_0eef1a83-de92-488b-840a-d2efda3cea34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentConstructionWorkInProgress_0eef1a83-de92-488b-840a-d2efda3cea34" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_faace153-170c-4a79-a0eb-d542c9a67203" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:to="loc_us-gaap_PublicUtilitiesPropertyPlantAndEquipmentNet_faace153-170c-4a79-a0eb-d542c9a67203" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherPropertyAndInvestments_95bce246-24b4-45d8-84f0-8a82716aca84" xlink:href="swx-20220630.xsd#swx_OtherPropertyAndInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:to="loc_swx_OtherPropertyAndInvestments_95bce246-24b4-45d8-84f0-8a82716aca84" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:to="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_a03f6cde-bd56-422c-a165-35dfdee1f27f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_a03f6cde-bd56-422c-a165-35dfdee1f27f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_ae7b520b-7d0a-4e4a-b3ab-f70822ce32c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_ae7b520b-7d0a-4e4a-b3ab-f70822ce32c0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_AccruedUtilityRevenue_ae6ac7fd-347c-46e3-8fd3-fa93b66f4d47" xlink:href="swx-20220630.xsd#swx_AccruedUtilityRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:to="loc_swx_AccruedUtilityRevenue_ae6ac7fd-347c-46e3-8fd3-fa93b66f4d47" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesReceivable_d44cc770-c3d7-4f3e-a691-3a184db40ac0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxesReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:to="loc_us-gaap_IncomeTaxesReceivable_d44cc770-c3d7-4f3e-a691-3a184db40ac0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredGasCost_50124438-c686-4b89-8fb1-f42588d85f0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredGasCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:to="loc_us-gaap_DeferredGasCost_50124438-c686-4b89-8fb1-f42588d85f0e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DueFromRelatedPartiesCurrent_04952d7f-4248-40d6-a3ba-baf330b2196e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DueFromRelatedPartiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:to="loc_us-gaap_DueFromRelatedPartiesCurrent_04952d7f-4248-40d6-a3ba-baf330b2196e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_61e8a5f7-15ad-415e-a318-3ec30878617d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_61e8a5f7-15ad-415e-a318-3ec30878617d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_7037a48d-f08d-4ce7-81e4-4fa62b0296b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_466bdd93-2b93-4966-8c23-37c4bf6907c8" xlink:to="loc_us-gaap_AssetsCurrent_7037a48d-f08d-4ce7-81e4-4fa62b0296b9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNoncurrentAbstract_cbdb9bf4-312a-4783-ba08-2fc287048e7d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:to="loc_us-gaap_AssetsNoncurrentAbstract_cbdb9bf4-312a-4783-ba08-2fc287048e7d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_86eaf614-7b7d-4c63-bb6a-d090cb24f493" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_cbdb9bf4-312a-4783-ba08-2fc287048e7d" xlink:to="loc_us-gaap_Goodwill_86eaf614-7b7d-4c63-bb6a-d090cb24f493" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_9795408b-7f3e-44a3-9023-f3a87a077043" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_cbdb9bf4-312a-4783-ba08-2fc287048e7d" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_9795408b-7f3e-44a3-9023-f3a87a077043" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment_5c8eab34-7102-422a-a8cf-cb968fa5c1e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsNoncurrentAbstract_cbdb9bf4-312a-4783-ba08-2fc287048e7d" xlink:to="loc_us-gaap_AssetsNoncurrentOtherThanNoncurrentInvestmentsAndPropertyPlantAndEquipment_5c8eab34-7102-422a-a8cf-cb968fa5c1e7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_6e7726f7-8e14-4036-9e17-50d4a5c6a2d8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_326e89bc-8ce5-4903-ba12-a520a77c5678" xlink:to="loc_us-gaap_Assets_6e7726f7-8e14-4036-9e17-50d4a5c6a2d8" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_d4b9196f-81ee-4696-ae89-e2df1bbdd0f2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7d0bb9e4-c2ca-45ce-b73e-635a846a2008" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_d4b9196f-81ee-4696-ae89-e2df1bbdd0f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CapitalizationLongtermDebtAndEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_d4b9196f-81ee-4696-ae89-e2df1bbdd0f2" xlink:to="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_64853229-fe87-461d-96be-fc424cc95652" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:to="loc_us-gaap_CommonStockValue_64853229-fe87-461d-96be-fc424cc95652" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_6998d2c8-2733-481f-9f2f-6ddedc588dc7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_6998d2c8-2733-481f-9f2f-6ddedc588dc7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_c3b37f99-fca7-49f0-99ab-6c4da5fa8014" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_c3b37f99-fca7-49f0-99ab-6c4da5fa8014" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_a22e119e-b4fd-4ee6-8db5-7ba4b41e7b5f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_a22e119e-b4fd-4ee6-8db5-7ba4b41e7b5f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_1183268d-6af4-45c8-935b-fe3dbd59d09a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:to="loc_us-gaap_StockholdersEquity_1183268d-6af4-45c8-935b-fe3dbd59d09a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_e6c1ed48-0ca1-4be7-899b-ff0b44f1cf52" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_e6c1ed48-0ca1-4be7-899b-ff0b44f1cf52" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalizationLongtermDebtAndEquity_799060d0-02dc-4676-8a15-2a83b7637a60" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CapitalizationLongtermDebtAndEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalizationLongtermDebtAndEquityAbstract_de049a20-4628-4743-837b-717b08b0b909" xlink:to="loc_us-gaap_CapitalizationLongtermDebtAndEquity_799060d0-02dc-4676-8a15-2a83b7637a60" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_d4b9196f-81ee-4696-ae89-e2df1bbdd0f2" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_d6619db3-73bf-48c0-a825-1c42f12d4a96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_LongTermDebtCurrent_d6619db3-73bf-48c0-a825-1c42f12d4a96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_970279cd-cefe-4084-819a-22eff70df58d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_ShortTermBorrowings_970279cd-cefe-4084-819a-22eff70df58d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_f08e2ed2-deb9-42d5-9147-b51a3bd0c329" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_AccountsPayableCurrent_f08e2ed2-deb9-42d5-9147-b51a3bd0c329" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_d516fdc5-c138-4c7c-b5f4-990b6b217e4f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_d516fdc5-c138-4c7c-b5f4-990b6b217e4f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_6bcb9ce6-1691-463c-97f2-27b070c27904" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_AccrualForTaxesOtherThanIncomeTaxesCurrent_6bcb9ce6-1691-463c-97f2-27b070c27904" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPayableCurrent_a6a665a6-e16e-4b7c-aa28-7711f8e091bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_InterestPayableCurrent_a6a665a6-e16e-4b7c-aa28-7711f8e091bc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DueToAffiliateCurrent_ce1c9b3f-59d7-4b11-87ca-1c3b7033786c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DueToAffiliateCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_DueToAffiliateCurrent_ce1c9b3f-59d7-4b11-87ca-1c3b7033786c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesCurrent_79b6a5ed-72ef-4bca-82bc-cb790c76dbcb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_OtherLiabilitiesCurrent_79b6a5ed-72ef-4bca-82bc-cb790c76dbcb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_ddf6817b-6f2d-4157-b65e-1d27415065af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_fae7fb11-92bd-48dc-924f-956ebf82995c" xlink:to="loc_us-gaap_LiabilitiesCurrent_ddf6817b-6f2d-4157-b65e-1d27415065af" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrentAbstract_9bfafbc8-ce5a-4061-b9f8-aafebd26d780" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_d4b9196f-81ee-4696-ae89-e2df1bbdd0f2" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrentAbstract_9bfafbc8-ce5a-4061-b9f8-aafebd26d780" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DeferredIncomeTaxesAndUnamortizedInvestmentTaxCredits_ac883c24-0646-4cbd-adaf-6d4dde223433" xlink:href="swx-20220630.xsd#swx_DeferredIncomeTaxesAndUnamortizedInvestmentTaxCredits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrentAbstract_9bfafbc8-ce5a-4061-b9f8-aafebd26d780" xlink:to="loc_swx_DeferredIncomeTaxesAndUnamortizedInvestmentTaxCredits_ac883c24-0646-4cbd-adaf-6d4dde223433" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAccruedLiabilitiesNoncurrent_9679a0e7-c09e-47f3-941b-85226e0b78a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherAccruedLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrentAbstract_9bfafbc8-ce5a-4061-b9f8-aafebd26d780" xlink:to="loc_us-gaap_OtherAccruedLiabilitiesNoncurrent_9679a0e7-c09e-47f3-941b-85226e0b78a6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredCreditsAndOtherLiabilitiesNoncurrent_a7e3a49a-217d-46d8-993e-ba25f34a847c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DeferredCreditsAndOtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrentAbstract_9bfafbc8-ce5a-4061-b9f8-aafebd26d780" xlink:to="loc_us-gaap_DeferredCreditsAndOtherLiabilitiesNoncurrent_a7e3a49a-217d-46d8-993e-ba25f34a847c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_99d5d0d5-65b8-4a73-a32e-073d7429b8f0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrentAbstract_9bfafbc8-ce5a-4061-b9f8-aafebd26d780" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_99d5d0d5-65b8-4a73-a32e-073d7429b8f0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_98e88b33-9f34-4ab7-93ea-2c738370fb0c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_d4b9196f-81ee-4696-ae89-e2df1bbdd0f2" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_98e88b33-9f34-4ab7-93ea-2c738370fb0c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_05fcb999-4b0e-423a-a8a6-0237b6381b49" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7d0bb9e4-c2ca-45ce-b73e-635a846a2008" xlink:to="loc_us-gaap_StatementTable_05fcb999-4b0e-423a-a8a6-0237b6381b49" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_80a29a46-140f-469a-b456-3ba5f74242f6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_05fcb999-4b0e-423a-a8a6-0237b6381b49" xlink:to="loc_dei_LegalEntityAxis_80a29a46-140f-469a-b456-3ba5f74242f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_80a29a46-140f-469a-b456-3ba5f74242f6_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_80a29a46-140f-469a-b456-3ba5f74242f6" xlink:to="loc_dei_EntityDomain_80a29a46-140f-469a-b456-3ba5f74242f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_c472019f-e943-43d2-b99f-f04c11411612" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_80a29a46-140f-469a-b456-3ba5f74242f6" xlink:to="loc_dei_EntityDomain_c472019f-e943-43d2-b99f-f04c11411612" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_6b3a1418-5879-43c0-8c94-6a6d92d80689" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_c472019f-e943-43d2-b99f-f04c11411612" xlink:to="loc_swx_SouthwestGasCorporationMember_6b3a1418-5879-43c0-8c94-6a6d92d80689" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFINCOMESouthwest" xlink:type="simple" xlink:href="swx-20220630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFINCOMESouthwest"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFINCOMESouthwest" xlink:type="extended" id="i0b1199469aa24144a65d0131e65b1a99_CONDENSEDCONSOLIDATEDSTATEMENTSOFINCOMESouthwest">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RegulatedOperatingRevenueGas_5963cdb6-7aa9-42b2-ab8d-d09749267c68" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RegulatedOperatingRevenueGas"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:to="loc_us-gaap_RegulatedOperatingRevenueGas_5963cdb6-7aa9-42b2-ab8d-d09749267c68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_a7a70f9f-4b65-4ffd-9a08-91302afd7545" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_a7a70f9f-4b65-4ffd-9a08-91302afd7545" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UtilitiesOperatingExpenseGasAndPetroleumPurchased_61859d19-9d38-4be8-8966-c50ebec9fa9c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UtilitiesOperatingExpenseGasAndPetroleumPurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_a7a70f9f-4b65-4ffd-9a08-91302afd7545" xlink:to="loc_us-gaap_UtilitiesOperatingExpenseGasAndPetroleumPurchased_61859d19-9d38-4be8-8966-c50ebec9fa9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations_d472d0b7-57d8-44b9-9dc9-f45352030999" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_a7a70f9f-4b65-4ffd-9a08-91302afd7545" xlink:to="loc_us-gaap_UtilitiesOperatingExpenseMaintenanceAndOperations_d472d0b7-57d8-44b9-9dc9-f45352030999" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_bb9001b0-5785-42f4-8a89-3cc0fef848f6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_a7a70f9f-4b65-4ffd-9a08-91302afd7545" xlink:to="loc_us-gaap_DepreciationAndAmortization_bb9001b0-5785-42f4-8a89-3cc0fef848f6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TaxesExcludingIncomeAndExciseTaxes_248e76ae-abce-47f0-a162-29e4f41dfdea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TaxesExcludingIncomeAndExciseTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_a7a70f9f-4b65-4ffd-9a08-91302afd7545" xlink:to="loc_us-gaap_TaxesExcludingIncomeAndExciseTaxes_248e76ae-abce-47f0-a162-29e4f41dfdea" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_8b79108b-edee-409b-8af0-8895e016b97d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_a7a70f9f-4b65-4ffd-9a08-91302afd7545" xlink:to="loc_us-gaap_CostsAndExpenses_8b79108b-edee-409b-8af0-8895e016b97d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_a0cc2ca5-b3e2-494a-9349-dd4bfa1fe6b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:to="loc_us-gaap_OperatingIncomeLoss_a0cc2ca5-b3e2-494a-9349-dd4bfa1fe6b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpenseAbstract_e4c30dbc-a41b-4973-88e6-d22a517d3b5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:to="loc_us-gaap_NonoperatingIncomeExpenseAbstract_e4c30dbc-a41b-4973-88e6-d22a517d3b5b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_084dc305-3326-4077-b2b1-94099238372d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_e4c30dbc-a41b-4973-88e6-d22a517d3b5b" xlink:to="loc_us-gaap_InterestExpense_084dc305-3326-4077-b2b1-94099238372d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_7ae37347-f3cc-4c87-87fd-989e8c497d38" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_e4c30dbc-a41b-4973-88e6-d22a517d3b5b" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_7ae37347-f3cc-4c87-87fd-989e8c497d38" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_75c6774c-8a37-4a03-8cca-d3a97494e645" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonoperatingIncomeExpenseAbstract_e4c30dbc-a41b-4973-88e6-d22a517d3b5b" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_75c6774c-8a37-4a03-8cca-d3a97494e645" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_36dbde30-dd35-4803-88b4-1b8642fdfedf" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_36dbde30-dd35-4803-88b4-1b8642fdfedf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_4091d1ab-7282-4bf0-91ac-857bf47c3530" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_4091d1ab-7282-4bf0-91ac-857bf47c3530" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_8bf8fccb-8aee-415c-84ce-d7067c61353c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:to="loc_us-gaap_NetIncomeLoss_8bf8fccb-8aee-415c-84ce-d7067c61353c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_c5a9ee49-8d1a-442c-875e-001aac108023" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_c8e25df9-a69b-4ad9-9add-94f1a3093d55" xlink:to="loc_us-gaap_StatementTable_c5a9ee49-8d1a-442c-875e-001aac108023" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_5a626bcd-8633-4092-a02f-2a3b79ac74f7" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_c5a9ee49-8d1a-442c-875e-001aac108023" xlink:to="loc_dei_LegalEntityAxis_5a626bcd-8633-4092-a02f-2a3b79ac74f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_5a626bcd-8633-4092-a02f-2a3b79ac74f7_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_5a626bcd-8633-4092-a02f-2a3b79ac74f7" xlink:to="loc_dei_EntityDomain_5a626bcd-8633-4092-a02f-2a3b79ac74f7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_b0dedb3c-fb5f-48c3-9038-07b43ffcc52d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_5a626bcd-8633-4092-a02f-2a3b79ac74f7" xlink:to="loc_dei_EntityDomain_b0dedb3c-fb5f-48c3-9038-07b43ffcc52d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_52a50000-4eda-477d-869a-76e526910f80" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_b0dedb3c-fb5f-48c3-9038-07b43ffcc52d" xlink:to="loc_swx_SouthwestGasCorporationMember_52a50000-4eda-477d-869a-76e526910f80" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMESouthwest" xlink:type="simple" xlink:href="swx-20220630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMESouthwest"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMESouthwest" xlink:type="extended" id="idba78192e88740ef921c3b8f295cb355_CONDENSEDCONSOLIDATEDSTATEMENTSOFCOMPREHENSIVEINCOMESouthwest">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_5d1115e5-34b3-462f-adee-31e4c599617c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:to="loc_us-gaap_ProfitLoss_5d1115e5-34b3-462f-adee-31e4c599617c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_7a6a21c0-e866-452d-8d1b-e7c14e71831d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_7a6a21c0-e866-452d-8d1b-e7c14e71831d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_20cfdfe2-08d0-4562-ba7e-ace432dae449" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_7a6a21c0-e866-452d-8d1b-e7c14e71831d" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_20cfdfe2-08d0-4562-ba7e-ace432dae449" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax_3af2568c-070f-4c86-9619-b578af15bd89" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_20cfdfe2-08d0-4562-ba7e-ace432dae449" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansNetUnamortizedGainLossArisingDuringPeriodNetOfTax_3af2568c-070f-4c86-9619-b578af15bd89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax_6933e5ea-dfc4-4ed8-a419-011f0e35fcde" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_20cfdfe2-08d0-4562-ba7e-ace432dae449" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAmortizationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetPriorServiceCostCreditNetOfTax_6933e5ea-dfc4-4ed8-a419-011f0e35fcde" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_09330efe-dcb2-4245-8d86-3cd3994de4fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_20cfdfe2-08d0-4562-ba7e-ace432dae449" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_09330efe-dcb2-4245-8d86-3cd3994de4fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherComprehensiveIncomeDefinedBenefitPlansRegulatoryAdjustmentNetOfTax_73d97e3e-3ced-4617-98bb-bdd2da30bdc9" xlink:href="swx-20220630.xsd#swx_OtherComprehensiveIncomeDefinedBenefitPlansRegulatoryAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_20cfdfe2-08d0-4562-ba7e-ace432dae449" xlink:to="loc_swx_OtherComprehensiveIncomeDefinedBenefitPlansRegulatoryAdjustmentNetOfTax_73d97e3e-3ced-4617-98bb-bdd2da30bdc9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_d8ccd00c-05a5-4d45-a7b4-5c2af63f18e8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPeriodIncreaseDecreaseAbstract_20cfdfe2-08d0-4562-ba7e-ace432dae449" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_d8ccd00c-05a5-4d45-a7b4-5c2af63f18e8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecreaseAbstract_cfc3955c-9464-45e7-92d5-5c9ca35840cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract_7a6a21c0-e866-452d-8d1b-e7c14e71831d" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecreaseAbstract_cfc3955c-9464-45e7-92d5-5c9ca35840cb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_66b13755-8a74-40be-abcb-8fab6af06ed6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecreaseAbstract_cfc3955c-9464-45e7-92d5-5c9ca35840cb" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_66b13755-8a74-40be-abcb-8fab6af06ed6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_d9fab0cb-22dc-45ba-b831-e7a8727c37e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecreaseAbstract_cfc3955c-9464-45e7-92d5-5c9ca35840cb" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_d9fab0cb-22dc-45ba-b831-e7a8727c37e7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_74459f36-6f27-4495-aca6-cf280c619f23" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_74459f36-6f27-4495-aca6-cf280c619f23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_97619c80-8b6d-420e-a767-f2ed8a745e18" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest_97619c80-8b6d-420e-a767-f2ed8a745e18" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_d6be5df4-5531-4451-8cb2-36d1d804bdff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_d6be5df4-5531-4451-8cb2-36d1d804bdff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_2d1aff3d-9f1f-4578-b841-c4b128b556f4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTaxAttributableToNoncontrollingInterest_2d1aff3d-9f1f-4578-b841-c4b128b556f4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_551882c9-6cd1-4b97-9cac-920bf61f91b3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_551882c9-6cd1-4b97-9cac-920bf61f91b3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_0cc9b0cf-259a-4c6a-8cba-dc03e0c8f9f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_8052365b-d1e5-4be3-9ba3-0570b39455d1" xlink:to="loc_us-gaap_StatementTable_0cc9b0cf-259a-4c6a-8cba-dc03e0c8f9f9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_9651b7a8-f97f-486d-be3a-137d81e6c71b" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_0cc9b0cf-259a-4c6a-8cba-dc03e0c8f9f9" xlink:to="loc_dei_LegalEntityAxis_9651b7a8-f97f-486d-be3a-137d81e6c71b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_9651b7a8-f97f-486d-be3a-137d81e6c71b_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_9651b7a8-f97f-486d-be3a-137d81e6c71b" xlink:to="loc_dei_EntityDomain_9651b7a8-f97f-486d-be3a-137d81e6c71b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_0c48a94d-c129-4654-b1fc-5a6141be431c" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_9651b7a8-f97f-486d-be3a-137d81e6c71b" xlink:to="loc_dei_EntityDomain_0c48a94d-c129-4654-b1fc-5a6141be431c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_d949273f-0bf5-45ea-bf56-3de347a7c04c" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_0c48a94d-c129-4654-b1fc-5a6141be431c" xlink:to="loc_swx_SouthwestGasCorporationMember_d949273f-0bf5-45ea-bf56-3de347a7c04c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWSSouthwest" xlink:type="simple" xlink:href="swx-20220630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWSSouthwest"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWSSouthwest" xlink:type="extended" id="i1a2fc83073564d26af8c31e173d6d72b_CONDENSEDCONSOLIDATEDSTATEMENTSOFCASHFLOWSSouthwest">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_4d56e0b4-9661-4759-8921-96f54f89c2d0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78cef581-b3bb-49eb-a60a-98752ae93400" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4d56e0b4-9661-4759-8921-96f54f89c2d0" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78cef581-b3bb-49eb-a60a-98752ae93400" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_4a9d6293-59de-476d-b8a8-aef370960556" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78cef581-b3bb-49eb-a60a-98752ae93400" xlink:to="loc_us-gaap_ProfitLoss_4a9d6293-59de-476d-b8a8-aef370960556" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78cef581-b3bb-49eb-a60a-98752ae93400" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_ab46b935-f1a6-4c76-b8b1-87de3af9393f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:to="loc_us-gaap_DepreciationAndAmortization_ab46b935-f1a6-4c76-b8b1-87de3af9393f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes_d8f40d39-5deb-4472-affd-9eea9a39bb6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInDeferredIncomeTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredIncomeTaxes_d8f40d39-5deb-4472-affd-9eea9a39bb6a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_7ef84c8f-6eed-49e9-aa73-6360a1f3b2ee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_7ef84c8f-6eed-49e9-aa73-6360a1f3b2ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_79821e9e-f907-43a3-933e-aafce6f3c0d1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:to="loc_us-gaap_IncreaseDecreaseInContractWithCustomerAsset_79821e9e-f907-43a3-933e-aafce6f3c0d1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredGasCost_623d218f-c882-4501-9b0e-4b03bb434acc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInDeferredGasCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredGasCost_623d218f-c882-4501-9b0e-4b03bb434acc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_ba4eb741-0db8-4d3c-adaa-647ea015b2f2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_ba4eb741-0db8-4d3c-adaa-647ea015b2f2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedTaxesPayable_10dc1439-b294-49a6-898d-40fd3454ee06" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInAccruedTaxesPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedTaxesPayable_10dc1439-b294-49a6-898d-40fd3454ee06" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssetsAndLiabilitiesNet_9b8f0735-e93e-44f3-90da-31cc241395c3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInOtherCurrentAssetsAndLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherCurrentAssetsAndLiabilitiesNet_9b8f0735-e93e-44f3-90da-31cc241395c3" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_058158f9-b80f-4af7-88cd-7ebc611a93d9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_7cb2f86e-19b5-42d9-b424-3e8d1332cfa7" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_058158f9-b80f-4af7-88cd-7ebc611a93d9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_481d1103-5909-4bce-9256-232824ab31b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:to="loc_us-gaap_ShareBasedCompensation_481d1103-5909-4bce-9256-232824ab31b7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction_33187f04-f393-4716-80bc-b7c43c934fd5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:to="loc_us-gaap_IncreaseDecreaseInAllowanceForEquityFundsUsedDuringConstruction_33187f04-f393-4716-80bc-b7c43c934fd5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_08f51952-40d1-454c-961a-e3d9aa728be5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_08f51952-40d1-454c-961a-e3d9aa728be5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_6053d68f-459c-4a1f-9c6f-ad54f010c9f9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_7a5868cd-5c60-400d-801a-a2cf61ff05af" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_6053d68f-459c-4a1f-9c6f-ad54f010c9f9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_4281e6c8-3f58-4261-8e62-1726a9a92a32" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_78cef581-b3bb-49eb-a60a-98752ae93400" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_4281e6c8-3f58-4261-8e62-1726a9a92a32" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ee8a68a-b202-495f-a334-41d18140c209" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4d56e0b4-9661-4759-8921-96f54f89c2d0" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ee8a68a-b202-495f-a334-41d18140c209" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_2bf8d6bc-0b1f-46a5-abf9-e13c2cb4c586" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ee8a68a-b202-495f-a334-41d18140c209" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_2bf8d6bc-0b1f-46a5-abf9-e13c2cb4c586" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_ChangesInCustomerAdvancesInvestingActivities_68b84563-3222-4948-9a89-b1397a466020" xlink:href="swx-20220630.xsd#swx_ChangesInCustomerAdvancesInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ee8a68a-b202-495f-a334-41d18140c209" xlink:to="loc_swx_ChangesInCustomerAdvancesInvestingActivities_68b84563-3222-4948-9a89-b1397a466020" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_5c229060-7f96-424c-8422-57bda19ad03b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ee8a68a-b202-495f-a334-41d18140c209" xlink:to="loc_us-gaap_PaymentsForProceedsFromOtherInvestingActivities_5c229060-7f96-424c-8422-57bda19ad03b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_6e2c45e2-1383-4b1b-a029-a872e5005576" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_4ee8a68a-b202-495f-a334-41d18140c209" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_6e2c45e2-1383-4b1b-a029-a872e5005576" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4d56e0b4-9661-4759-8921-96f54f89c2d0" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromContributionsFromParent_5a027361-4cd3-413e-a306-dd61528c196a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromContributionsFromParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_us-gaap_ProceedsFromContributionsFromParent_5a027361-4cd3-413e-a306-dd61528c196a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDividendsCommonStock_15c62afd-736e-48c9-8210-eaef24c4e56d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsOfDividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_us-gaap_PaymentsOfDividendsCommonStock_15c62afd-736e-48c9-8210-eaef24c4e56d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_c8736218-baf6-4e32-9124-fe53a8f25e5a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_c8736218-baf6-4e32-9124-fe53a8f25e5a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_98fd4add-d648-4e83-a764-8346b14f055d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_98fd4add-d648-4e83-a764-8346b14f055d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_ProceedsFromRepaymentsOfLinesOfCreditAndCommercialPaper_e6ef9090-1894-49df-b6d5-555b6d1dc70c" xlink:href="swx-20220630.xsd#swx_ProceedsFromRepaymentsOfLinesOfCreditAndCommercialPaper"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_swx_ProceedsFromRepaymentsOfLinesOfCreditAndCommercialPaper_e6ef9090-1894-49df-b6d5-555b6d1dc70c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebt_effe764f-49db-4497-a11a-8cb94d1dfd10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromRepaymentsOfShortTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_us-gaap_ProceedsFromRepaymentsOfShortTermDebt_effe764f-49db-4497-a11a-8cb94d1dfd10" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_90556c1f-17b0-453f-9b70-870924956e40" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_90556c1f-17b0-453f-9b70-870924956e40" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_85d54434-196c-41da-9bbd-4d2d06990d86" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromPaymentsForOtherFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_85d54434-196c-41da-9bbd-4d2d06990d86" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_cdf1d310-39d0-4c35-b571-99e64ac6df20" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_7251b8bb-9162-4985-a04c-7d6523f7e26a" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_cdf1d310-39d0-4c35-b571-99e64ac6df20" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_f7e8eec3-b773-4e48-9d34-fc71c9a4a79c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4d56e0b4-9661-4759-8921-96f54f89c2d0" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_f7e8eec3-b773-4e48-9d34-fc71c9a4a79c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_2ed6c200-5d35-49ca-a120-4f81b88b6e1e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4d56e0b4-9661-4759-8921-96f54f89c2d0" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_2ed6c200-5d35-49ca-a120-4f81b88b6e1e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_f7cdd30c-0103-4ce7-9709-5a756e835f54" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_23871a09-c2e0-43f1-9873-0d9912a542ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4d56e0b4-9661-4759-8921-96f54f89c2d0" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_23871a09-c2e0-43f1-9873-0d9912a542ba" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_83e2ff2d-704c-4be5-bd47-6635488f9c4d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_23871a09-c2e0-43f1-9873-0d9912a542ba" xlink:to="loc_us-gaap_InterestPaidNet_83e2ff2d-704c-4be5-bd47-6635488f9c4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaidNet_dbf0cae1-4633-4a5d-ae5e-82b742745a80" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeTaxesPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_23871a09-c2e0-43f1-9873-0d9912a542ba" xlink:to="loc_us-gaap_IncomeTaxesPaidNet_dbf0cae1-4633-4a5d-ae5e-82b742745a80" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_f474aeda-e0cd-462d-89df-ea102de76071" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_4d56e0b4-9661-4759-8921-96f54f89c2d0" xlink:to="loc_us-gaap_StatementTable_f474aeda-e0cd-462d-89df-ea102de76071" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_8b4da91a-218e-48c1-98f0-8d02fa75884e" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_f474aeda-e0cd-462d-89df-ea102de76071" xlink:to="loc_dei_LegalEntityAxis_8b4da91a-218e-48c1-98f0-8d02fa75884e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_8b4da91a-218e-48c1-98f0-8d02fa75884e_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_8b4da91a-218e-48c1-98f0-8d02fa75884e" xlink:to="loc_dei_EntityDomain_8b4da91a-218e-48c1-98f0-8d02fa75884e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3e1b425a-ee4e-45eb-9121-c56028037bac" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_8b4da91a-218e-48c1-98f0-8d02fa75884e" xlink:to="loc_dei_EntityDomain_3e1b425a-ee4e-45eb-9121-c56028037bac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_e7445b49-582b-4ced-98a7-6cd6434a6976" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_3e1b425a-ee4e-45eb-9121-c56028037bac" xlink:to="loc_swx_SouthwestGasCorporationMember_e7445b49-582b-4ced-98a7-6cd6434a6976" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITYSouthwest" xlink:type="simple" xlink:href="swx-20220630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITYSouthwest"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITYSouthwest" xlink:type="extended" id="ia6d4baec48414c16ae2ef127b1bbba34_CONDENSEDCONSOLIDATEDSTATEMENTSOFEQUITYSouthwest">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_7a2ecb6a-dd51-4aeb-be46-3a654de277a9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7a2ecb6a-dd51-4aeb-be46-3a654de277a9" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_d80047e2-b98f-406f-99ca-d46b6306e101" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_d80047e2-b98f-406f-99ca-d46b6306e101" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_d0db6412-79e8-43e1-8e35-35ff716131c2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_d0db6412-79e8-43e1-8e35-35ff716131c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_486b88ba-ded2-46e8-83e4-32d9083138a5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:to="loc_us-gaap_NetIncomeLossIncludingPortionAttributableToNonredeemableNoncontrollingInterest_486b88ba-ded2-46e8-83e4-32d9083138a5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_cd9bf4b2-922b-4cb2-afc2-03c0a69dd02f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_cd9bf4b2-922b-4cb2-afc2-03c0a69dd02f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_AdjustmentsToAdditionalPaidInCapitalContributionsFromParent_44c55045-6823-4de1-a60a-1b0d0e873732" xlink:href="swx-20220630.xsd#swx_AdjustmentsToAdditionalPaidInCapitalContributionsFromParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:to="loc_swx_AdjustmentsToAdditionalPaidInCapitalContributionsFromParent_44c55045-6823-4de1-a60a-1b0d0e873732" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStock_8081298a-a4fc-4f40-933e-c536ec86911c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:to="loc_us-gaap_DividendsCommonStock_8081298a-a4fc-4f40-933e-c536ec86911c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTaxOther_4965aea1-b732-4115-b51e-5b70d45248b5" xlink:href="swx-20220630.xsd#swx_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTaxOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:to="loc_swx_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTaxOther_4965aea1-b732-4115-b51e-5b70d45248b5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_1fdf9154-2540-429d-b0a1-2074078c5dbe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0f21c95d-75f8-47b8-842b-c1677f50d819" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_1fdf9154-2540-429d-b0a1-2074078c5dbe" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_e052118b-1188-4883-b8be-fddb8fdf3784" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_bdb1c656-c863-479e-a76c-11fb28e61171" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_281466b0-a309-4000-8822-8079d325bb50" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7a2ecb6a-dd51-4aeb-be46-3a654de277a9" xlink:to="loc_us-gaap_StatementTable_281466b0-a309-4000-8822-8079d325bb50" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_94e8e677-48c4-4129-993d-53d36b0b44e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_281466b0-a309-4000-8822-8079d325bb50" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_94e8e677-48c4-4129-993d-53d36b0b44e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_94e8e677-48c4-4129-993d-53d36b0b44e7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_94e8e677-48c4-4129-993d-53d36b0b44e7" xlink:to="loc_us-gaap_EquityComponentDomain_94e8e677-48c4-4129-993d-53d36b0b44e7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_46df422d-3551-4dc3-88f4-9ffd1808b9cb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_94e8e677-48c4-4129-993d-53d36b0b44e7" xlink:to="loc_us-gaap_EquityComponentDomain_46df422d-3551-4dc3-88f4-9ffd1808b9cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_08d024b5-0a5d-422a-8b26-5f25420d4aa3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_46df422d-3551-4dc3-88f4-9ffd1808b9cb" xlink:to="loc_us-gaap_CommonStockMember_08d024b5-0a5d-422a-8b26-5f25420d4aa3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_25d57e5b-2903-4ea8-9d30-8cb630934ef3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_46df422d-3551-4dc3-88f4-9ffd1808b9cb" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_25d57e5b-2903-4ea8-9d30-8cb630934ef3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_4bd12779-4449-4894-a764-dc662e948fef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_46df422d-3551-4dc3-88f4-9ffd1808b9cb" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_4bd12779-4449-4894-a764-dc662e948fef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_d6dfd5c6-9577-4632-b2ec-9ef57c2bc26a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_46df422d-3551-4dc3-88f4-9ffd1808b9cb" xlink:to="loc_us-gaap_RetainedEarningsMember_d6dfd5c6-9577-4632-b2ec-9ef57c2bc26a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_e99f2725-3036-49c7-a4e1-c5e363a1aac6" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_281466b0-a309-4000-8822-8079d325bb50" xlink:to="loc_dei_LegalEntityAxis_e99f2725-3036-49c7-a4e1-c5e363a1aac6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_e99f2725-3036-49c7-a4e1-c5e363a1aac6_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_e99f2725-3036-49c7-a4e1-c5e363a1aac6" xlink:to="loc_dei_EntityDomain_e99f2725-3036-49c7-a4e1-c5e363a1aac6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_076724dc-e972-404e-976d-62f632cc0610" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_e99f2725-3036-49c7-a4e1-c5e363a1aac6" xlink:to="loc_dei_EntityDomain_076724dc-e972-404e-976d-62f632cc0610" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_66c10e7e-acc1-43cd-8ca2-bba088262fb2" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_076724dc-e972-404e-976d-62f632cc0610" xlink:to="loc_swx_SouthwestGasCorporationMember_66c10e7e-acc1-43cd-8ca2-bba088262fb2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesNarrativesDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#BackgroundOrganizationandSummaryofSignificantAccountingPoliciesNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesNarrativesDetails" xlink:type="extended" id="i5b841d7994224543b84f570be81afbe8_BackgroundOrganizationandSummaryofSignificantAccountingPoliciesNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:href="swx-20220630.xsd#swx_SignificantAccountingPoliciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_EntitySeparationCompletionPeriod_f02915d2-a145-49d4-8796-c89ee1334717" xlink:href="swx-20220630.xsd#swx_EntitySeparationCompletionPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_EntitySeparationCompletionPeriod_f02915d2-a145-49d4-8796-c89ee1334717" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_NumberOfNewBoardOfDirectorsAppointed_7301800d-c68e-4997-a521-7fdc58c81515" xlink:href="swx-20220630.xsd#swx_NumberOfNewBoardOfDirectorsAppointed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_NumberOfNewBoardOfDirectorsAppointed_7301800d-c68e-4997-a521-7fdc58c81515" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_NumberOfStrategicTransactionsCommitteeDirectors_dae795d6-fe67-4424-a543-0c43c67148cc" xlink:href="swx-20220630.xsd#swx_NumberOfStrategicTransactionsCommitteeDirectors"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_NumberOfStrategicTransactionsCommitteeDirectors_dae795d6-fe67-4424-a543-0c43c67148cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RightsAgreementAmendmentBeneficialOwnershipPercentage_01fa74df-52c5-4464-8c0d-8499ebba4096" xlink:href="swx-20220630.xsd#swx_RightsAgreementAmendmentBeneficialOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_RightsAgreementAmendmentBeneficialOwnershipPercentage_01fa74df-52c5-4464-8c0d-8499ebba4096" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RightsAgreementAmendmentUpdatedTenderPricePerShare_7ff0e583-ba28-40db-b09a-2b96125175fd" xlink:href="swx-20220630.xsd#swx_RightsAgreementAmendmentUpdatedTenderPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_RightsAgreementAmendmentUpdatedTenderPricePerShare_7ff0e583-ba28-40db-b09a-2b96125175fd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_57c0d387-c6f3-4eb4-a7f0-76ec87437780" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_57c0d387-c6f3-4eb4-a7f0-76ec87437780" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CapitalExpendituresIncurredButNotYetPaidIncreaseDecrease_cc0ef2a6-231b-499c-859a-40667d0bc6f1" xlink:href="swx-20220630.xsd#swx_CapitalExpendituresIncurredButNotYetPaidIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_CapitalExpendituresIncurredButNotYetPaidIncreaseDecrease_cc0ef2a6-231b-499c-859a-40667d0bc6f1" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DeferredPurchasedGasCostsRecoveredOrRefundedPeriod_c992a0bc-2c12-4501-9e03-028946a9993b" xlink:href="swx-20220630.xsd#swx_DeferredPurchasedGasCostsRecoveredOrRefundedPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_DeferredPurchasedGasCostsRecoveredOrRefundedPeriod_c992a0bc-2c12-4501-9e03-028946a9993b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaterialsSuppliesAndOther_086d412f-3180-431c-8af2-3cd3427bad8e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MaterialsSuppliesAndOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_MaterialsSuppliesAndOther_086d412f-3180-431c-8af2-3cd3427bad8e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_AccruedPurchasedGasCosts_aefedab9-95f7-433a-96be-2125d6104645" xlink:href="swx-20220630.xsd#swx_AccruedPurchasedGasCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_AccruedPurchasedGasCosts_aefedab9-95f7-433a-96be-2125d6104645" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillImpairmentLoss_fdeee288-e86e-486b-b493-f0fadff0d9a4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_GoodwillImpairmentLoss_fdeee288-e86e-486b-b493-f0fadff0d9a4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrent_6bcb9191-8e79-4f5a-8df7-6b6f9a930dae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DividendsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_DividendsPayableCurrent_6bcb9191-8e79-4f5a-8df7-6b6f9a930dae" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_887659d2-2271-4f35-b939-15ff14cf54e7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_887659d2-2271-4f35-b939-15ff14cf54e7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfRedeemableNoncontrollingInterest_e61dd2bc-a1de-4127-8da7-dccd17ff135f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsForRepurchaseOfRedeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfRedeemableNoncontrollingInterest_e61dd2bc-a1de-4127-8da7-dccd17ff135f" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RedeemableNoncontrollingInterestPercentageRedeemed_b3f8b0d0-2601-4f44-a435-df95f17afe26" xlink:href="swx-20220630.xsd#swx_RedeemableNoncontrollingInterestPercentageRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_RedeemableNoncontrollingInterestPercentageRedeemed_b3f8b0d0-2601-4f44-a435-df95f17afe26" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestChangeInRedemptionValue_33f5e927-89f6-4e90-9475-0a4a81ffdedb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestChangeInRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_MinorityInterestChangeInRedemptionValue_33f5e927-89f6-4e90-9475-0a4a81ffdedb" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LossContingencySelfInsuredRetentionAmount_62471f6e-576f-4f1e-80ec-6270d5c1b87c" xlink:href="swx-20220630.xsd#swx_LossContingencySelfInsuredRetentionAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_LossContingencySelfInsuredRetentionAmount_62471f6e-576f-4f1e-80ec-6270d5c1b87c" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LossContingencyThresholdAmountAboveSelfInsuredRetention_f02a1459-544d-4188-a9d3-51b8e28fa36c" xlink:href="swx-20220630.xsd#swx_LossContingencyThresholdAmountAboveSelfInsuredRetention"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_LossContingencyThresholdAmountAboveSelfInsuredRetention_f02a1459-544d-4188-a9d3-51b8e28fa36c" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LossContingencyNumberOfIndividualsInjured_3303f46a-a854-490e-a54c-c5dd872738c5" xlink:href="swx-20220630.xsd#swx_LossContingencyNumberOfIndividualsInjured"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_LossContingencyNumberOfIndividualsInjured_3303f46a-a854-490e-a54c-c5dd872738c5" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LossContingencyMaximumExposure_16482879-67b8-4648-b33e-ebd0ef63b084" xlink:href="swx-20220630.xsd#swx_LossContingencyMaximumExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_LossContingencyMaximumExposure_16482879-67b8-4648-b33e-ebd0ef63b084" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualAtCarryingValue_0a1b09d1-f9d4-4c07-b1fb-f17b3e5f7133" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingencyAccrualAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_LossContingencyAccrualAtCarryingValue_0a1b09d1-f9d4-4c07-b1fb-f17b3e5f7133" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingencyAccrualCarryingValuePeriodIncreaseDecrease_a3edd8b6-0ab6-4552-9d13-204a8b38f8ac" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LossContingencyAccrualCarryingValuePeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_us-gaap_LossContingencyAccrualCarryingValuePeriodIncreaseDecrease_a3edd8b6-0ab6-4552-9d13-204a8b38f8ac" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SignificantAccountingPoliciesTable_cb11e9cc-d0af-495f-8aee-0b70a157a268" xlink:href="swx-20220630.xsd#swx_SignificantAccountingPoliciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_a3befad6-31dd-43da-ab83-08dd0557c768" xlink:to="loc_swx_SignificantAccountingPoliciesTable_cb11e9cc-d0af-495f-8aee-0b70a157a268" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_008a1940-4ac5-4048-b8fb-ed068106651d" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_swx_SignificantAccountingPoliciesTable_cb11e9cc-d0af-495f-8aee-0b70a157a268" xlink:to="loc_srt_RangeAxis_008a1940-4ac5-4048-b8fb-ed068106651d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_008a1940-4ac5-4048-b8fb-ed068106651d_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_008a1940-4ac5-4048-b8fb-ed068106651d" xlink:to="loc_srt_RangeMember_008a1940-4ac5-4048-b8fb-ed068106651d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_b648b41a-6b8a-45d4-b2e0-ad0de3ae796e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_008a1940-4ac5-4048-b8fb-ed068106651d" xlink:to="loc_srt_RangeMember_b648b41a-6b8a-45d4-b2e0-ad0de3ae796e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_4f8c7a5f-691e-44c0-b070-89a3c9720d53" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b648b41a-6b8a-45d4-b2e0-ad0de3ae796e" xlink:to="loc_srt_MinimumMember_4f8c7a5f-691e-44c0-b070-89a3c9720d53" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_6e513913-6581-4e4d-960c-7263ea055510" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_b648b41a-6b8a-45d4-b2e0-ad0de3ae796e" xlink:to="loc_srt_MaximumMember_6e513913-6581-4e4d-960c-7263ea055510" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_dcbc5e8a-246c-4652-80c6-ee49cb7d53a8" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_swx_SignificantAccountingPoliciesTable_cb11e9cc-d0af-495f-8aee-0b70a157a268" xlink:to="loc_dei_LegalEntityAxis_dcbc5e8a-246c-4652-80c6-ee49cb7d53a8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_dcbc5e8a-246c-4652-80c6-ee49cb7d53a8_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_dcbc5e8a-246c-4652-80c6-ee49cb7d53a8" xlink:to="loc_dei_EntityDomain_dcbc5e8a-246c-4652-80c6-ee49cb7d53a8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_38e92b99-81b0-4153-aa68-77631e1a243a" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_dcbc5e8a-246c-4652-80c6-ee49cb7d53a8" xlink:to="loc_dei_EntityDomain_38e92b99-81b0-4153-aa68-77631e1a243a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiGroupInc.Member_c52d0735-5262-4081-aa61-dfcdc024e4c6" xlink:href="swx-20220630.xsd#swx_CenturiGroupInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_38e92b99-81b0-4153-aa68-77631e1a243a" xlink:to="loc_swx_CenturiGroupInc.Member_c52d0735-5262-4081-aa61-dfcdc024e4c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_1d37bb25-1545-4c0c-895a-cfa379a890f1" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_38e92b99-81b0-4153-aa68-77631e1a243a" xlink:to="loc_swx_SouthwestGasCorporationMember_1d37bb25-1545-4c0c-895a-cfa379a890f1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_PreviousOwnerOfLinetecMember_1a85a455-c75a-47bc-be6d-59b1f8cb19b3" xlink:href="swx-20220630.xsd#swx_PreviousOwnerOfLinetecMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_38e92b99-81b0-4153-aa68-77631e1a243a" xlink:to="loc_swx_PreviousOwnerOfLinetecMember_1a85a455-c75a-47bc-be6d-59b1f8cb19b3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CertainMembersOfRiggsDistlerManagementMember_731c5c8d-0db2-4f5e-a294-77275213cd8c" xlink:href="swx-20220630.xsd#swx_CertainMembersOfRiggsDistlerManagementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_38e92b99-81b0-4153-aa68-77631e1a243a" xlink:to="loc_swx_CertainMembersOfRiggsDistlerManagementMember_731c5c8d-0db2-4f5e-a294-77275213cd8c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_7352e029-5364-415d-a549-e6d770b5a9e5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashAndCashEquivalentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_swx_SignificantAccountingPoliciesTable_cb11e9cc-d0af-495f-8aee-0b70a157a268" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_7352e029-5364-415d-a549-e6d770b5a9e5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_7352e029-5364-415d-a549-e6d770b5a9e5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_7352e029-5364-415d-a549-e6d770b5a9e5" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_7352e029-5364-415d-a549-e6d770b5a9e5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_84cc6abd-6781-42f1-9132-25c6dc488c5c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_7352e029-5364-415d-a549-e6d770b5a9e5" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_84cc6abd-6781-42f1-9132-25c6dc488c5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MoneyMarketFundsMember_2cc147dd-a823-4c69-a243-919fe36e6d3f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MoneyMarketFundsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_84cc6abd-6781-42f1-9132-25c6dc488c5c" xlink:to="loc_us-gaap_MoneyMarketFundsMember_2cc147dd-a823-4c69-a243-919fe36e6d3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_028b73f3-6891-4d5b-b5e0-1e65757afa57" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_swx_SignificantAccountingPoliciesTable_cb11e9cc-d0af-495f-8aee-0b70a157a268" xlink:to="loc_srt_OwnershipAxis_028b73f3-6891-4d5b-b5e0-1e65757afa57" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_028b73f3-6891-4d5b-b5e0-1e65757afa57_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_028b73f3-6891-4d5b-b5e0-1e65757afa57" xlink:to="loc_srt_OwnershipDomain_028b73f3-6891-4d5b-b5e0-1e65757afa57_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_0b177646-527c-48d4-9684-2c3285660b98" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_028b73f3-6891-4d5b-b5e0-1e65757afa57" xlink:to="loc_srt_OwnershipDomain_0b177646-527c-48d4-9684-2c3285660b98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LinetecServicesLLCMember_b324c60f-12ae-4c7a-a792-cb9ec49e81bb" xlink:href="swx-20220630.xsd#swx_LinetecServicesLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_0b177646-527c-48d4-9684-2c3285660b98" xlink:to="loc_swx_LinetecServicesLLCMember_b324c60f-12ae-4c7a-a792-cb9ec49e81bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DrumMember_012f6265-3fd7-4d91-953d-1e54c534b83c" xlink:href="swx-20220630.xsd#swx_DrumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_0b177646-527c-48d4-9684-2c3285660b98" xlink:to="loc_swx_DrumMember_012f6265-3fd7-4d91-953d-1e54c534b83c" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesScheduleofOtherPropertyandInvestmentsDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#BackgroundOrganizationandSummaryofSignificantAccountingPoliciesScheduleofOtherPropertyandInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesScheduleofOtherPropertyandInvestmentsDetails" xlink:type="extended" id="i23f4e107351c44adb4ed2409e44a1576_BackgroundOrganizationandSummaryofSignificantAccountingPoliciesScheduleofOtherPropertyandInvestmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_02b81fe0-2b73-4fea-8035-06ccc6723587" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashSurrenderValueOfLifeInsurance_bcb84ded-6e9e-4dca-8fdd-29520b1c4edd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CashSurrenderValueOfLifeInsurance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_02b81fe0-2b73-4fea-8035-06ccc6723587" xlink:to="loc_us-gaap_CashSurrenderValueOfLifeInsurance_bcb84ded-6e9e-4dca-8fdd-29520b1c4edd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentOtherNet_fb8b9948-46c2-434d-9ba7-d58b549d66fc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PropertyPlantAndEquipmentOtherNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_02b81fe0-2b73-4fea-8035-06ccc6723587" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentOtherNet_fb8b9948-46c2-434d-9ba7-d58b549d66fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherPropertyAndInvestmentsNet_d57a63cf-df26-4347-8828-dde549293436" xlink:href="swx-20220630.xsd#swx_OtherPropertyAndInvestmentsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_02b81fe0-2b73-4fea-8035-06ccc6723587" xlink:to="loc_swx_OtherPropertyAndInvestmentsNet_d57a63cf-df26-4347-8828-dde549293436" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_PropertyPlantEquipmentAndIntangibleAssetsGross_119ed50b-81ca-499c-84c1-4fe8c51ab6e8" xlink:href="swx-20220630.xsd#swx_PropertyPlantEquipmentAndIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_02b81fe0-2b73-4fea-8035-06ccc6723587" xlink:to="loc_swx_PropertyPlantEquipmentAndIntangibleAssetsGross_119ed50b-81ca-499c-84c1-4fe8c51ab6e8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_f5df130f-d718-4490-845c-56c734b8be60" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_02b81fe0-2b73-4fea-8035-06ccc6723587" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_f5df130f-d718-4490-845c-56c734b8be60" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1c42eae8-a461-42f3-bd8d-2689c7898a73" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_02b81fe0-2b73-4fea-8035-06ccc6723587" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1c42eae8-a461-42f3-bd8d-2689c7898a73" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_c2ecd8de-210d-451b-a05c-77d4edfbd3da" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1c42eae8-a461-42f3-bd8d-2689c7898a73" xlink:to="loc_dei_LegalEntityAxis_c2ecd8de-210d-451b-a05c-77d4edfbd3da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_c2ecd8de-210d-451b-a05c-77d4edfbd3da_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_c2ecd8de-210d-451b-a05c-77d4edfbd3da" xlink:to="loc_dei_EntityDomain_c2ecd8de-210d-451b-a05c-77d4edfbd3da_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_cbf24efe-c1af-46a6-a07d-d4f7eb9ec817" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_c2ecd8de-210d-451b-a05c-77d4edfbd3da" xlink:to="loc_dei_EntityDomain_cbf24efe-c1af-46a6-a07d-d4f7eb9ec817" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_0783d65f-9e53-4692-922c-a798049cdbf6" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_cbf24efe-c1af-46a6-a07d-d4f7eb9ec817" xlink:to="loc_swx_SouthwestGasCorporationMember_0783d65f-9e53-4692-922c-a798049cdbf6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesScheduleofGoodwillDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#BackgroundOrganizationandSummaryofSignificantAccountingPoliciesScheduleofGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesScheduleofGoodwillDetails" xlink:type="extended" id="i19594bef3e704e3f942832a6b7545124_BackgroundOrganizationandSummaryofSignificantAccountingPoliciesScheduleofGoodwillDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_0713bda2-2d1f-4d9a-88c6-0f18c730f164" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_a861455f-668f-4303-aecb-cf98accca866" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_0713bda2-2d1f-4d9a-88c6-0f18c730f164" xlink:to="loc_us-gaap_GoodwillRollForward_a861455f-668f-4303-aecb-cf98accca866" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_270dedc5-ca84-496d-8fce-ce588de110d8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_a861455f-668f-4303-aecb-cf98accca866" xlink:to="loc_us-gaap_Goodwill_270dedc5-ca84-496d-8fce-ce588de110d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_bf8e88c1-6334-47e3-a4ba-b850f2a18abc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_a861455f-668f-4303-aecb-cf98accca866" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_bf8e88c1-6334-47e3-a4ba-b850f2a18abc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_a13d5404-a8b3-4bb1-ac53-445920f67ab4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_a861455f-668f-4303-aecb-cf98accca866" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_a13d5404-a8b3-4bb1-ac53-445920f67ab4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_66443b6e-0035-4f9a-965d-22b1fb8ad9d4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_cf053e89-0e7a-44c3-86c5-6c525ff502de" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_0713bda2-2d1f-4d9a-88c6-0f18c730f164" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_cf053e89-0e7a-44c3-86c5-6c525ff502de" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_85e30560-9dcb-45a8-8b6d-b835367ae1f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_cf053e89-0e7a-44c3-86c5-6c525ff502de" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_85e30560-9dcb-45a8-8b6d-b835367ae1f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_85e30560-9dcb-45a8-8b6d-b835367ae1f3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_85e30560-9dcb-45a8-8b6d-b835367ae1f3" xlink:to="loc_us-gaap_SegmentDomain_85e30560-9dcb-45a8-8b6d-b835367ae1f3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_5bbc69be-8072-48e9-875e-1c12dfae6c7e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_85e30560-9dcb-45a8-8b6d-b835367ae1f3" xlink:to="loc_us-gaap_SegmentDomain_5bbc69be-8072-48e9-875e-1c12dfae6c7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_NaturalGasDistributionSegmentMember_ef81dbf7-0cfb-48fc-9d7c-4d58987f8200" xlink:href="swx-20220630.xsd#swx_NaturalGasDistributionSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5bbc69be-8072-48e9-875e-1c12dfae6c7e" xlink:to="loc_swx_NaturalGasDistributionSegmentMember_ef81dbf7-0cfb-48fc-9d7c-4d58987f8200" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_UtilityInfrastructureServicesSegmentMember_af77bef8-2eed-446c-859d-2764190d5306" xlink:href="swx-20220630.xsd#swx_UtilityInfrastructureServicesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5bbc69be-8072-48e9-875e-1c12dfae6c7e" xlink:to="loc_swx_UtilityInfrastructureServicesSegmentMember_af77bef8-2eed-446c-859d-2764190d5306" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_PipelineAndStorageSegmentMember_1416b1fa-619b-466b-a82c-eb1474a873bf" xlink:href="swx-20220630.xsd#swx_PipelineAndStorageSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_5bbc69be-8072-48e9-875e-1c12dfae6c7e" xlink:to="loc_swx_PipelineAndStorageSegmentMember_1416b1fa-619b-466b-a82c-eb1474a873bf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_cb81b58e-7bd0-4fa8-a6af-2986ab429abe" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_cf053e89-0e7a-44c3-86c5-6c525ff502de" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_cb81b58e-7bd0-4fa8-a6af-2986ab429abe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cb81b58e-7bd0-4fa8-a6af-2986ab429abe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_cb81b58e-7bd0-4fa8-a6af-2986ab429abe" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cb81b58e-7bd0-4fa8-a6af-2986ab429abe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5a0f66f5-a105-4446-b76c-329d173130ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_cb81b58e-7bd0-4fa8-a6af-2986ab429abe" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5a0f66f5-a105-4446-b76c-329d173130ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RiggsDistlerMember_fcdb56e2-3f12-4de5-a39e-addb4569f3c8" xlink:href="swx-20220630.xsd#swx_RiggsDistlerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5a0f66f5-a105-4446-b76c-329d173130ef" xlink:to="loc_swx_RiggsDistlerMember_fcdb56e2-3f12-4de5-a39e-addb4569f3c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_MountainWestMember_f2a75a44-50a3-49d8-a985-3bf420d9c060" xlink:href="swx-20220630.xsd#swx_MountainWestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5a0f66f5-a105-4446-b76c-329d173130ef" xlink:to="loc_swx_MountainWestMember_f2a75a44-50a3-49d8-a985-3bf420d9c060" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesOtherIncomeDeductionsDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#BackgroundOrganizationandSummaryofSignificantAccountingPoliciesOtherIncomeDeductionsDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesOtherIncomeDeductionsDetails" xlink:type="extended" id="i853124f322f745edb13b91a40d6b07f6_BackgroundOrganizationandSummaryofSignificantAccountingPoliciesOtherIncomeDeductionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_srt_CondensedIncomeStatementsCaptionsLineItems_ac00f666-1305-49b4-acc7-2bcf14e7732f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CondensedIncomeStatementsCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNonoperatingIncomeExpenseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_CondensedIncomeStatementsCaptionsLineItems_ac00f666-1305-49b4-acc7-2bcf14e7732f" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue_cddd00d7-9d5a-42ec-aa17-3c36eb1acd87" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:to="loc_us-gaap_LifeInsuranceCorporateOrBankOwnedChangeInValue_cddd00d7-9d5a-42ec-aa17-3c36eb1acd87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOther_db6cc844-a3e6-49b2-a7ce-be8363e8079f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_InterestIncomeOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:to="loc_us-gaap_InterestIncomeOther_db6cc844-a3e6-49b2-a7ce-be8363e8079f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity_66724622-a7df-429c-acc8-a2a1c423da26" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:to="loc_us-gaap_PublicUtilitiesAllowanceForFundsUsedDuringConstructionCapitalizedCostOfEquity_66724622-a7df-429c-acc8-a2a1c423da26" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit_c520d0ed-621a-4018-8a7d-608e0298a9de" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:to="loc_us-gaap_DefinedBenefitPlanActuarialGainLossImmediateRecognitionAsComponentInNetPeriodicBenefitCostCredit_c520d0ed-621a-4018-8a7d-608e0298a9de" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_MiscellaneousIncomeExpense_3f5644e1-ada2-4d79-9ea6-2df20754603e" xlink:href="swx-20220630.xsd#swx_MiscellaneousIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:to="loc_swx_MiscellaneousIncomeExpense_3f5644e1-ada2-4d79-9ea6-2df20754603e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized_1ce31ae3-0d7b-4030-9ee2-8580812c6fb5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:to="loc_us-gaap_ForeignCurrencyTransactionGainLossRealized_1ce31ae3-0d7b-4030-9ee2-8580812c6fb5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromEquityMethodInvestments_82a17047-2a42-420b-a529-52cac1c8b779" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_IncomeLossFromEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:to="loc_us-gaap_IncomeLossFromEquityMethodInvestments_82a17047-2a42-420b-a529-52cac1c8b779" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_4d8b715d-b757-40a2-8294-4f1109d38f18" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherNonoperatingIncomeExpenseAbstract_7a494895-299c-4127-86f8-394b945201a7" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_4d8b715d-b757-40a2-8294-4f1109d38f18" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CondensedIncomeStatementTable_b214c499-b52c-4def-abef-a5819cda1e38" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_CondensedIncomeStatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_CondensedIncomeStatementsCaptionsLineItems_ac00f666-1305-49b4-acc7-2bcf14e7732f" xlink:to="loc_srt_CondensedIncomeStatementTable_b214c499-b52c-4def-abef-a5819cda1e38" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_5e4efd42-6299-4978-8349-f24ab1e3a874" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_CondensedIncomeStatementTable_b214c499-b52c-4def-abef-a5819cda1e38" xlink:to="loc_dei_LegalEntityAxis_5e4efd42-6299-4978-8349-f24ab1e3a874" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_5e4efd42-6299-4978-8349-f24ab1e3a874_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_5e4efd42-6299-4978-8349-f24ab1e3a874" xlink:to="loc_dei_EntityDomain_5e4efd42-6299-4978-8349-f24ab1e3a874_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_b4be3493-205d-40ff-8d32-ef856d4d934d" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_5e4efd42-6299-4978-8349-f24ab1e3a874" xlink:to="loc_dei_EntityDomain_b4be3493-205d-40ff-8d32-ef856d4d934d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_cef1755b-aa74-42ec-bd98-2da7d78caaf2" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_b4be3493-205d-40ff-8d32-ef856d4d934d" xlink:to="loc_swx_SouthwestGasCorporationMember_cef1755b-aa74-42ec-bd98-2da7d78caaf2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesSummaryofRedeemableNoncontrollingInterestDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#BackgroundOrganizationandSummaryofSignificantAccountingPoliciesSummaryofRedeemableNoncontrollingInterestDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/BackgroundOrganizationandSummaryofSignificantAccountingPoliciesSummaryofRedeemableNoncontrollingInterestDetails" xlink:type="extended" id="i2e9a1e7617394f9298a4e579d084d810_BackgroundOrganizationandSummaryofSignificantAccountingPoliciesSummaryofRedeemableNoncontrollingInterestDetails">
    <link:loc xlink:type="locator" xlink:label="loc_swx_SignificantAccountingPoliciesLineItems_450127f5-fde4-47bc-a4e8-9d3e914de85c" xlink:href="swx-20220630.xsd#swx_SignificantAccountingPoliciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_MovementInRedeemableNoncontrollingInterestRollForward_734ccb61-203f-4d1a-8300-8688b768dd7a" xlink:href="swx-20220630.xsd#swx_MovementInRedeemableNoncontrollingInterestRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_450127f5-fde4-47bc-a4e8-9d3e914de85c" xlink:to="loc_swx_MovementInRedeemableNoncontrollingInterestRollForward_734ccb61-203f-4d1a-8300-8688b768dd7a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_b1ef2f6f-d058-41ad-bcab-00a5d42bafc1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_MovementInRedeemableNoncontrollingInterestRollForward_734ccb61-203f-4d1a-8300-8688b768dd7a" xlink:to="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_b1ef2f6f-d058-41ad-bcab-00a5d42bafc1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest_8c5a58fd-1fa0-42a2-bd0c-001f8e5b5b0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_MovementInRedeemableNoncontrollingInterestRollForward_734ccb61-203f-4d1a-8300-8688b768dd7a" xlink:to="loc_us-gaap_NetIncomeLossAttributableToRedeemableNoncontrollingInterest_8c5a58fd-1fa0-42a2-bd0c-001f8e5b5b0e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestChangeInRedemptionValue_7ae292b1-ca17-46c5-920d-6077cc0cac72" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestChangeInRedemptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_MovementInRedeemableNoncontrollingInterestRollForward_734ccb61-203f-4d1a-8300-8688b768dd7a" xlink:to="loc_us-gaap_MinorityInterestChangeInRedemptionValue_7ae292b1-ca17-46c5-920d-6077cc0cac72" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromRedemptions_3665f162-4429-4276-bb47-500822d404cc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestDecreaseFromRedemptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_swx_MovementInRedeemableNoncontrollingInterestRollForward_734ccb61-203f-4d1a-8300-8688b768dd7a" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromRedemptions_3665f162-4429-4276-bb47-500822d404cc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount_663ffaf0-196a-461e-90dd-7ef1c1aeaa8a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RedeemableNoncontrollingInterestEquityCarryingAmount"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SignificantAccountingPoliciesTable_c346f3f5-0c12-48ff-8f7e-8882fd612f86" xlink:href="swx-20220630.xsd#swx_SignificantAccountingPoliciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_swx_SignificantAccountingPoliciesLineItems_450127f5-fde4-47bc-a4e8-9d3e914de85c" xlink:to="loc_swx_SignificantAccountingPoliciesTable_c346f3f5-0c12-48ff-8f7e-8882fd612f86" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_f4615907-949b-4d2e-bde9-0f0c931c48bb" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_swx_SignificantAccountingPoliciesTable_c346f3f5-0c12-48ff-8f7e-8882fd612f86" xlink:to="loc_srt_OwnershipAxis_f4615907-949b-4d2e-bde9-0f0c931c48bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_f4615907-949b-4d2e-bde9-0f0c931c48bb_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_f4615907-949b-4d2e-bde9-0f0c931c48bb" xlink:to="loc_srt_OwnershipDomain_f4615907-949b-4d2e-bde9-0f0c931c48bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_14d71669-c0b6-48ad-8eed-fbe93b47777f" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_f4615907-949b-4d2e-bde9-0f0c931c48bb" xlink:to="loc_srt_OwnershipDomain_14d71669-c0b6-48ad-8eed-fbe93b47777f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LinetecServicesLLCMember_1a0d0d0e-4932-465c-af47-a4b259286457" xlink:href="swx-20220630.xsd#swx_LinetecServicesLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_14d71669-c0b6-48ad-8eed-fbe93b47777f" xlink:to="loc_swx_LinetecServicesLLCMember_1a0d0d0e-4932-465c-af47-a4b259286457" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DrumMember_e85631cc-017e-42d6-844c-5d98f89f74f2" xlink:href="swx-20220630.xsd#swx_DrumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_14d71669-c0b6-48ad-8eed-fbe93b47777f" xlink:to="loc_swx_DrumMember_e85631cc-017e-42d6-844c-5d98f89f74f2" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/ComponentsofNetPeriodicBenefitCostDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#ComponentsofNetPeriodicBenefitCostDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/ComponentsofNetPeriodicBenefitCostDetails" xlink:type="extended" id="i5dd86265a69148edaa639c3d3cd48cb2_ComponentsofNetPeriodicBenefitCostDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_4d9fc806-58cd-4015-96fe-ed83fd91bd0b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanServiceCost_bd6cc7a0-8acf-4210-acdf-5489b4fb7872" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanServiceCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_4d9fc806-58cd-4015-96fe-ed83fd91bd0b" xlink:to="loc_us-gaap_DefinedBenefitPlanServiceCost_bd6cc7a0-8acf-4210-acdf-5489b4fb7872" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanInterestCost_2d7bd63f-af52-4b97-9bde-1ad624657ac3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanInterestCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_4d9fc806-58cd-4015-96fe-ed83fd91bd0b" xlink:to="loc_us-gaap_DefinedBenefitPlanInterestCost_2d7bd63f-af52-4b97-9bde-1ad624657ac3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_41925b1c-cb30-46c6-91bd-bd05fb7c4b13" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_4d9fc806-58cd-4015-96fe-ed83fd91bd0b" xlink:to="loc_us-gaap_DefinedBenefitPlanExpectedReturnOnPlanAssets_41925b1c-cb30-46c6-91bd-bd05fb7c4b13" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_a1ce82d2-de1c-44d6-9fd7-ed3457ce1347" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_4d9fc806-58cd-4015-96fe-ed83fd91bd0b" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfGainsLosses_a1ce82d2-de1c-44d6-9fd7-ed3457ce1347" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_1949559e-2222-4197-97d0-b8ea947166fa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_4d9fc806-58cd-4015-96fe-ed83fd91bd0b" xlink:to="loc_us-gaap_DefinedBenefitPlanAmortizationOfPriorServiceCostCredit_1949559e-2222-4197-97d0-b8ea947166fa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_d6e4950b-15ee-4007-8bda-dd0d77855d1b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_4d9fc806-58cd-4015-96fe-ed83fd91bd0b" xlink:to="loc_us-gaap_DefinedBenefitPlanNetPeriodicBenefitCost_d6e4950b-15ee-4007-8bda-dd0d77855d1b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c7f9abcd-67e6-4ae5-a7ac-e39772ed690b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_4d9fc806-58cd-4015-96fe-ed83fd91bd0b" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c7f9abcd-67e6-4ae5-a7ac-e39772ed690b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeAxis_d67a31e1-607f-4ed3-9274-c692726d5e04" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_c7f9abcd-67e6-4ae5-a7ac-e39772ed690b" xlink:to="loc_us-gaap_RetirementPlanTypeAxis_d67a31e1-607f-4ed3-9274-c692726d5e04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_d67a31e1-607f-4ed3-9274-c692726d5e04_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_d67a31e1-607f-4ed3-9274-c692726d5e04" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_d67a31e1-607f-4ed3-9274-c692726d5e04_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetirementPlanTypeDomain_c721e71e-8af6-4a0f-8f25-ea60efa12af8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RetirementPlanTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RetirementPlanTypeAxis_d67a31e1-607f-4ed3-9274-c692726d5e04" xlink:to="loc_us-gaap_RetirementPlanTypeDomain_c721e71e-8af6-4a0f-8f25-ea60efa12af8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPensionPlansDefinedBenefitMember_db1e0b7b-03c0-4a0c-bd5e-8a5f61c9195c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherPensionPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_c721e71e-8af6-4a0f-8f25-ea60efa12af8" xlink:to="loc_us-gaap_OtherPensionPlansDefinedBenefitMember_db1e0b7b-03c0-4a0c-bd5e-8a5f61c9195c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember_4befa9e5-eaf8-44c3-a9e3-40d1daa7b766" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_c721e71e-8af6-4a0f-8f25-ea60efa12af8" xlink:to="loc_us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember_4befa9e5-eaf8-44c3-a9e3-40d1daa7b766" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_15fe886d-05ec-4d82-87cb-57d1b4231843" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RetirementPlanTypeDomain_c721e71e-8af6-4a0f-8f25-ea60efa12af8" xlink:to="loc_us-gaap_OtherPostretirementBenefitPlansDefinedBenefitMember_15fe886d-05ec-4d82-87cb-57d1b4231843" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/RevenueScheduleofRegulatedOperationsRevenuesNaturalGasDistributionSegmentDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#RevenueScheduleofRegulatedOperationsRevenuesNaturalGasDistributionSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/RevenueScheduleofRegulatedOperationsRevenuesNaturalGasDistributionSegmentDetails" xlink:type="extended" id="ib0d33bdb0aea45479c8d8711f7aaf01e_RevenueScheduleofRegulatedOperationsRevenuesNaturalGasDistributionSegmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_5c0e6a0e-06ac-4c78-a88a-4d0a6ba76682" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d67b7795-9eb5-4a69-9766-a7e62c2dd6d0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_5c0e6a0e-06ac-4c78-a88a-4d0a6ba76682" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d67b7795-9eb5-4a69-9766-a7e62c2dd6d0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_AlternativeRevenueProgramRevenuesDeferrals_9ca7f99d-6972-4af5-95cb-942af24f16a3" xlink:href="swx-20220630.xsd#swx_AlternativeRevenueProgramRevenuesDeferrals"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_5c0e6a0e-06ac-4c78-a88a-4d0a6ba76682" xlink:to="loc_swx_AlternativeRevenueProgramRevenuesDeferrals_9ca7f99d-6972-4af5-95cb-942af24f16a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherRevenue_4a0f77e7-f318-43ea-83b7-5c94418ee4aa" xlink:href="swx-20220630.xsd#swx_OtherRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_5c0e6a0e-06ac-4c78-a88a-4d0a6ba76682" xlink:to="loc_swx_OtherRevenue_4a0f77e7-f318-43ea-83b7-5c94418ee4aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RegulatedOperatingRevenueGas_4c12887e-d4c1-4157-8798-45d767b19339" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RegulatedOperatingRevenueGas"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_5c0e6a0e-06ac-4c78-a88a-4d0a6ba76682" xlink:to="loc_us-gaap_RegulatedOperatingRevenueGas_4c12887e-d4c1-4157-8798-45d767b19339" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_ce48c13f-44dc-4020-8649-93120d3f01ad" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_5c0e6a0e-06ac-4c78-a88a-4d0a6ba76682" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_ce48c13f-44dc-4020-8649-93120d3f01ad" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_9ef2dac6-3623-49b9-b303-7f2258cf4f20" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_ce48c13f-44dc-4020-8649-93120d3f01ad" xlink:to="loc_srt_MajorCustomersAxis_9ef2dac6-3623-49b9-b303-7f2258cf4f20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_9ef2dac6-3623-49b9-b303-7f2258cf4f20_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_9ef2dac6-3623-49b9-b303-7f2258cf4f20" xlink:to="loc_srt_NameOfMajorCustomerDomain_9ef2dac6-3623-49b9-b303-7f2258cf4f20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_92553653-fe8a-4854-8dec-5ce5fcaed896" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_9ef2dac6-3623-49b9-b303-7f2258cf4f20" xlink:to="loc_srt_NameOfMajorCustomerDomain_92553653-fe8a-4854-8dec-5ce5fcaed896" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_ResidentialMember_8ded1c25-4a36-496b-9e9d-c60e3437f2ad" xlink:href="swx-20220630.xsd#swx_ResidentialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_92553653-fe8a-4854-8dec-5ce5fcaed896" xlink:to="loc_swx_ResidentialMember_8ded1c25-4a36-496b-9e9d-c60e3437f2ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SmallCommercialMember_fc6e9984-a2e2-470a-ae82-47719b169d6d" xlink:href="swx-20220630.xsd#swx_SmallCommercialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_92553653-fe8a-4854-8dec-5ce5fcaed896" xlink:to="loc_swx_SmallCommercialMember_fc6e9984-a2e2-470a-ae82-47719b169d6d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LargeCommercialMember_242c2cc9-5685-483f-9d3c-727f8b7fab23" xlink:href="swx-20220630.xsd#swx_LargeCommercialMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_92553653-fe8a-4854-8dec-5ce5fcaed896" xlink:to="loc_swx_LargeCommercialMember_242c2cc9-5685-483f-9d3c-727f8b7fab23" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_IndustrialOrOtherMember_f77d8976-db81-471f-ae61-35a4cd5fa9c7" xlink:href="swx-20220630.xsd#swx_IndustrialOrOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_92553653-fe8a-4854-8dec-5ce5fcaed896" xlink:to="loc_swx_IndustrialOrOtherMember_f77d8976-db81-471f-ae61-35a4cd5fa9c7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_TransportationMember_f25056a3-f894-4634-b5d7-b942f9caca4e" xlink:href="swx-20220630.xsd#swx_TransportationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_92553653-fe8a-4854-8dec-5ce5fcaed896" xlink:to="loc_swx_TransportationMember_f25056a3-f894-4634-b5d7-b942f9caca4e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_144d547c-8473-43a4-b3c8-0578034a4587" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_ce48c13f-44dc-4020-8649-93120d3f01ad" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_144d547c-8473-43a4-b3c8-0578034a4587" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_144d547c-8473-43a4-b3c8-0578034a4587_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_144d547c-8473-43a4-b3c8-0578034a4587" xlink:to="loc_us-gaap_SegmentDomain_144d547c-8473-43a4-b3c8-0578034a4587_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_3c605172-fca8-452d-92fd-0cf8e1862165" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_144d547c-8473-43a4-b3c8-0578034a4587" xlink:to="loc_us-gaap_SegmentDomain_3c605172-fca8-452d-92fd-0cf8e1862165" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_NaturalGasDistributionSegmentMember_5eef8d15-402c-44b1-b561-6700ea0cc6c2" xlink:href="swx-20220630.xsd#swx_NaturalGasDistributionSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_3c605172-fca8-452d-92fd-0cf8e1862165" xlink:to="loc_swx_NaturalGasDistributionSegmentMember_5eef8d15-402c-44b1-b561-6700ea0cc6c2" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/RevenueScheduleofRegulatedOperationsRevenuesUtilityInfrastructureServicesSegmentDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#RevenueScheduleofRegulatedOperationsRevenuesUtilityInfrastructureServicesSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/RevenueScheduleofRegulatedOperationsRevenuesUtilityInfrastructureServicesSegmentDetails" xlink:type="extended" id="i033525cb65f64236bff523c91cb7348a_RevenueScheduleofRegulatedOperationsRevenuesUtilityInfrastructureServicesSegmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_4bf5bbbf-51b9-4e91-ba64-07144a8590ea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_4c6450a7-ba0f-47ec-81fb-ec8e668acc5b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_4bf5bbbf-51b9-4e91-ba64-07144a8590ea" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_4c6450a7-ba0f-47ec-81fb-ec8e668acc5b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_4e058e09-edc8-4ee6-bc33-adee99e37174" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_4bf5bbbf-51b9-4e91-ba64-07144a8590ea" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_4e058e09-edc8-4ee6-bc33-adee99e37174" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_6d53c6e9-de50-478a-bd32-bf22b943700b" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_4e058e09-edc8-4ee6-bc33-adee99e37174" xlink:to="loc_srt_ProductOrServiceAxis_6d53c6e9-de50-478a-bd32-bf22b943700b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_6d53c6e9-de50-478a-bd32-bf22b943700b_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_6d53c6e9-de50-478a-bd32-bf22b943700b" xlink:to="loc_srt_ProductsAndServicesDomain_6d53c6e9-de50-478a-bd32-bf22b943700b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_dda20732-cded-4409-9e4a-4682d5ae8396" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_6d53c6e9-de50-478a-bd32-bf22b943700b" xlink:to="loc_srt_ProductsAndServicesDomain_dda20732-cded-4409-9e4a-4682d5ae8396" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_GasInfrastructureServicesMember_2884abed-e050-4798-b948-4eddb55a7c33" xlink:href="swx-20220630.xsd#swx_GasInfrastructureServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dda20732-cded-4409-9e4a-4682d5ae8396" xlink:to="loc_swx_GasInfrastructureServicesMember_2884abed-e050-4798-b948-4eddb55a7c33" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_ElectricPowerInfrastructureServicesMember_876414c9-eb83-4fb3-bec8-96b84c797cdb" xlink:href="swx-20220630.xsd#swx_ElectricPowerInfrastructureServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dda20732-cded-4409-9e4a-4682d5ae8396" xlink:to="loc_swx_ElectricPowerInfrastructureServicesMember_876414c9-eb83-4fb3-bec8-96b84c797cdb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherInfrastructureServicesMember_a6965adf-f52d-407a-8e55-92faa87226d4" xlink:href="swx-20220630.xsd#swx_OtherInfrastructureServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_dda20732-cded-4409-9e4a-4682d5ae8396" xlink:to="loc_swx_OtherInfrastructureServicesMember_a6965adf-f52d-407a-8e55-92faa87226d4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_df401910-56f0-4e06-8e77-001fc61ebcd1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerBasisOfPricingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_4e058e09-edc8-4ee6-bc33-adee99e37174" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_df401910-56f0-4e06-8e77-001fc61ebcd1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_df401910-56f0-4e06-8e77-001fc61ebcd1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_df401910-56f0-4e06-8e77-001fc61ebcd1" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_df401910-56f0-4e06-8e77-001fc61ebcd1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_0308ef04-f499-46f2-a38a-87e8297a559c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerBasisOfPricingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingAxis_df401910-56f0-4e06-8e77-001fc61ebcd1" xlink:to="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_0308ef04-f499-46f2-a38a-87e8297a559c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_MasterServicesAgreementMember_e561947a-6a27-45b4-a2f0-4869e9b2191d" xlink:href="swx-20220630.xsd#swx_MasterServicesAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_0308ef04-f499-46f2-a38a-87e8297a559c" xlink:to="loc_swx_MasterServicesAgreementMember_e561947a-6a27-45b4-a2f0-4869e9b2191d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BidContractMember_8f249c83-890f-421c-be99-fff57f627cbf" xlink:href="swx-20220630.xsd#swx_BidContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_0308ef04-f499-46f2-a38a-87e8297a559c" xlink:to="loc_swx_BidContractMember_8f249c83-890f-421c-be99-fff57f627cbf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_UnitPricedContractsMember_4180bfba-622b-4edb-8fdb-81054f4d6ec3" xlink:href="swx-20220630.xsd#swx_UnitPricedContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_0308ef04-f499-46f2-a38a-87e8297a559c" xlink:to="loc_swx_UnitPricedContractsMember_4180bfba-622b-4edb-8fdb-81054f4d6ec3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedPriceContractMember_deb1726d-da22-4153-b18b-c5825e13ff41" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FixedPriceContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_0308ef04-f499-46f2-a38a-87e8297a559c" xlink:to="loc_us-gaap_FixedPriceContractMember_deb1726d-da22-4153-b18b-c5825e13ff41" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TimeAndMaterialsContractMember_2fd1277e-f595-4c46-9298-557daec01db7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_TimeAndMaterialsContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContractWithCustomerBasisOfPricingDomain_0308ef04-f499-46f2-a38a-87e8297a559c" xlink:to="loc_us-gaap_TimeAndMaterialsContractMember_2fd1277e-f595-4c46-9298-557daec01db7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_04ad1294-990c-461c-b566-f6fb2435f0bd" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_4e058e09-edc8-4ee6-bc33-adee99e37174" xlink:to="loc_dei_LegalEntityAxis_04ad1294-990c-461c-b566-f6fb2435f0bd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_04ad1294-990c-461c-b566-f6fb2435f0bd_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_04ad1294-990c-461c-b566-f6fb2435f0bd" xlink:to="loc_dei_EntityDomain_04ad1294-990c-461c-b566-f6fb2435f0bd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_06871493-1d1d-4492-8044-c44205746869" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_04ad1294-990c-461c-b566-f6fb2435f0bd" xlink:to="loc_dei_EntityDomain_06871493-1d1d-4492-8044-c44205746869" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiGroupInc.Member_92d8768a-94dd-47bf-8257-f4cafc2e6a33" xlink:href="swx-20220630.xsd#swx_CenturiGroupInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_06871493-1d1d-4492-8044-c44205746869" xlink:to="loc_swx_CenturiGroupInc.Member_92d8768a-94dd-47bf-8257-f4cafc2e6a33" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis_4efcca4b-df4a-4fbd-ba06-0c75b15dfb3c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_4e058e09-edc8-4ee6-bc33-adee99e37174" xlink:to="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis_4efcca4b-df4a-4fbd-ba06-0c75b15dfb3c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsForErrorCorrectionDomain_4efcca4b-df4a-4fbd-ba06-0c75b15dfb3c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsForErrorCorrectionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis_4efcca4b-df4a-4fbd-ba06-0c75b15dfb3c" xlink:to="loc_us-gaap_AdjustmentsForErrorCorrectionDomain_4efcca4b-df4a-4fbd-ba06-0c75b15dfb3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsForErrorCorrectionDomain_b8f79831-93f9-4ced-b324-955fc1d81dff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AdjustmentsForErrorCorrectionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ErrorCorrectionsAndPriorPeriodAdjustmentsRestatementByRestatementPeriodAndAmountAxis_4efcca4b-df4a-4fbd-ba06-0c75b15dfb3c" xlink:to="loc_us-gaap_AdjustmentsForErrorCorrectionDomain_b8f79831-93f9-4ced-b324-955fc1d81dff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_UnderstatementOfMasterServicesCategoryMember_b127e4c0-d1f8-43ba-ba44-79ea2209fa49" xlink:href="swx-20220630.xsd#swx_UnderstatementOfMasterServicesCategoryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsForErrorCorrectionDomain_b8f79831-93f9-4ced-b324-955fc1d81dff" xlink:to="loc_swx_UnderstatementOfMasterServicesCategoryMember_b127e4c0-d1f8-43ba-ba44-79ea2209fa49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OverstatementOfBidContractCategoryMember_98bfd745-f1ac-47a9-84ad-e7fa9989a2b5" xlink:href="swx-20220630.xsd#swx_OverstatementOfBidContractCategoryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsForErrorCorrectionDomain_b8f79831-93f9-4ced-b324-955fc1d81dff" xlink:to="loc_swx_OverstatementOfBidContractCategoryMember_98bfd745-f1ac-47a9-84ad-e7fa9989a2b5" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/RevenueNarrativesDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#RevenueNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/RevenueNarrativesDetails" xlink:type="extended" id="ic9b9210e52c244e2ae195eb4c16166ee_RevenueNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3965adac-acb7-4313-b4c3-b3c5f562409d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3965adac-acb7-4313-b4c3-b3c5f562409d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RevenueRecognitionNumberOfContractsWithOriginalDurationMoreThanOneYear_309333c2-6e68-4a76-a01f-e4be9df19b3e" xlink:href="swx-20220630.xsd#swx_RevenueRecognitionNumberOfContractsWithOriginalDurationMoreThanOneYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_swx_RevenueRecognitionNumberOfContractsWithOriginalDurationMoreThanOneYear_309333c2-6e68-4a76-a01f-e4be9df19b3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_9d132b2f-9625-4b62-a6fe-561e7e440af3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_9d132b2f-9625-4b62-a6fe-561e7e440af3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_e6deedd2-78ea-4184-8bb9-196bd2a20bee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_e6deedd2-78ea-4184-8bb9-196bd2a20bee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f6829586-98d4-4caa-8700-6a11650753dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f6829586-98d4-4caa-8700-6a11650753dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_998dc89f-7e30-4d0e-b6ba-915154a7a3a3" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f6829586-98d4-4caa-8700-6a11650753dd" xlink:to="loc_dei_LegalEntityAxis_998dc89f-7e30-4d0e-b6ba-915154a7a3a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_998dc89f-7e30-4d0e-b6ba-915154a7a3a3_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_998dc89f-7e30-4d0e-b6ba-915154a7a3a3" xlink:to="loc_dei_EntityDomain_998dc89f-7e30-4d0e-b6ba-915154a7a3a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3c1714dd-0a2a-40f8-8941-7a1412023e9f" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_998dc89f-7e30-4d0e-b6ba-915154a7a3a3" xlink:to="loc_dei_EntityDomain_3c1714dd-0a2a-40f8-8941-7a1412023e9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiGroupInc.Member_46014f43-9a83-4c5a-9e28-a967c2b5b742" xlink:href="swx-20220630.xsd#swx_CenturiGroupInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_3c1714dd-0a2a-40f8-8941-7a1412023e9f" xlink:to="loc_swx_CenturiGroupInc.Member_46014f43-9a83-4c5a-9e28-a967c2b5b742" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_86f283e8-fe81-4cf3-aec6-42e883888373" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f6829586-98d4-4caa-8700-6a11650753dd" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_86f283e8-fe81-4cf3-aec6-42e883888373" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/RevenueNarrativesDetails_1" xlink:type="simple" xlink:href="swx-20220630.xsd#RevenueNarrativesDetails_1"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/RevenueNarrativesDetails_1" xlink:type="extended" id="i9a1d5f35c4e54a769548a9945b30c36d_RevenueNarrativesDetails_1">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3965adac-acb7-4313-b4c3-b3c5f562409d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_3965adac-acb7-4313-b4c3-b3c5f562409d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RevenueRecognitionNumberOfContractsWithOriginalDurationMoreThanOneYear_309333c2-6e68-4a76-a01f-e4be9df19b3e" xlink:href="swx-20220630.xsd#swx_RevenueRecognitionNumberOfContractsWithOriginalDurationMoreThanOneYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_swx_RevenueRecognitionNumberOfContractsWithOriginalDurationMoreThanOneYear_309333c2-6e68-4a76-a01f-e4be9df19b3e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_9d132b2f-9625-4b62-a6fe-561e7e440af3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_9d132b2f-9625-4b62-a6fe-561e7e440af3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_e6deedd2-78ea-4184-8bb9-196bd2a20bee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_e6deedd2-78ea-4184-8bb9-196bd2a20bee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f6829586-98d4-4caa-8700-6a11650753dd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_a49d12aa-cfd6-456f-950c-8ea50e892a42" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f6829586-98d4-4caa-8700-6a11650753dd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_998dc89f-7e30-4d0e-b6ba-915154a7a3a3" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_f6829586-98d4-4caa-8700-6a11650753dd" xlink:to="loc_dei_LegalEntityAxis_998dc89f-7e30-4d0e-b6ba-915154a7a3a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_998dc89f-7e30-4d0e-b6ba-915154a7a3a3_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_998dc89f-7e30-4d0e-b6ba-915154a7a3a3" xlink:to="loc_dei_EntityDomain_998dc89f-7e30-4d0e-b6ba-915154a7a3a3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3c1714dd-0a2a-40f8-8941-7a1412023e9f" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_998dc89f-7e30-4d0e-b6ba-915154a7a3a3" xlink:to="loc_dei_EntityDomain_3c1714dd-0a2a-40f8-8941-7a1412023e9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiGroupInc.Member_46014f43-9a83-4c5a-9e28-a967c2b5b742" xlink:href="swx-20220630.xsd#swx_CenturiGroupInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_3c1714dd-0a2a-40f8-8941-7a1412023e9f" xlink:to="loc_swx_CenturiGroupInc.Member_46014f43-9a83-4c5a-9e28-a967c2b5b742" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/RevenueScheduleofUtilityInfrastructureServicesContractsReceivableDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#RevenueScheduleofUtilityInfrastructureServicesContractsReceivableDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/RevenueScheduleofUtilityInfrastructureServicesContractsReceivableDetails" xlink:type="extended" id="ic5e50d81f655487fa55f28a7009b45ea_RevenueScheduleofUtilityInfrastructureServicesContractsReceivableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_e0d67209-81be-407f-a474-feedcf460441" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetGross_c68da7c9-9ede-473d-8a48-535d090935c5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerAssetGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_e0d67209-81be-407f-a474-feedcf460441" xlink:to="loc_us-gaap_ContractWithCustomerAssetGross_c68da7c9-9ede-473d-8a48-535d090935c5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetAccumulatedAllowanceForCreditLoss_10fa8d4d-76d1-46ea-940a-8b7de4b3cb94" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerAssetAccumulatedAllowanceForCreditLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_e0d67209-81be-407f-a474-feedcf460441" xlink:to="loc_us-gaap_ContractWithCustomerAssetAccumulatedAllowanceForCreditLoss_10fa8d4d-76d1-46ea-940a-8b7de4b3cb94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNet_799b9139-6d24-4e12-8222-cdc68c01b728" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ContractWithCustomerAssetNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_e0d67209-81be-407f-a474-feedcf460441" xlink:to="loc_us-gaap_ContractWithCustomerAssetNet_799b9139-6d24-4e12-8222-cdc68c01b728" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_1786740c-206e-465b-ae36-3e2128bf9a92" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_e0d67209-81be-407f-a474-feedcf460441" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_1786740c-206e-465b-ae36-3e2128bf9a92" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_604d8e54-beea-4791-b6aa-3918d132f394" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_1786740c-206e-465b-ae36-3e2128bf9a92" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_604d8e54-beea-4791-b6aa-3918d132f394" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_604d8e54-beea-4791-b6aa-3918d132f394_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_604d8e54-beea-4791-b6aa-3918d132f394" xlink:to="loc_us-gaap_SegmentDomain_604d8e54-beea-4791-b6aa-3918d132f394_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_a1b23389-af35-475b-b025-fc7509b6eba5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_604d8e54-beea-4791-b6aa-3918d132f394" xlink:to="loc_us-gaap_SegmentDomain_a1b23389-af35-475b-b025-fc7509b6eba5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_UtilityInfrastructureServicesSegmentMember_da05de58-8971-45c2-aecd-101e36db9ba2" xlink:href="swx-20220630.xsd#swx_UtilityInfrastructureServicesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_a1b23389-af35-475b-b025-fc7509b6eba5" xlink:to="loc_swx_UtilityInfrastructureServicesSegmentMember_da05de58-8971-45c2-aecd-101e36db9ba2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_8841c768-a5e5-4eeb-a707-4caf898531a6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_1786740c-206e-465b-ae36-3e2128bf9a92" xlink:to="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_8841c768-a5e5-4eeb-a707-4caf898531a6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_8841c768-a5e5-4eeb-a707-4caf898531a6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_8841c768-a5e5-4eeb-a707-4caf898531a6" xlink:to="loc_us-gaap_ReceivableTypeDomain_8841c768-a5e5-4eeb-a707-4caf898531a6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReceivableTypeDomain_6a4b1ce3-3cd5-4b7c-9fee-ec5cc473c8ea" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReceivableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis_8841c768-a5e5-4eeb-a707-4caf898531a6" xlink:to="loc_us-gaap_ReceivableTypeDomain_6a4b1ce3-3cd5-4b7c-9fee-ec5cc473c8ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BilledOnCompletedContractsAndContractsInProgressMember_ced13c52-94f7-44de-9ee2-6a6641e789e6" xlink:href="swx-20220630.xsd#swx_BilledOnCompletedContractsAndContractsInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_6a4b1ce3-3cd5-4b7c-9fee-ec5cc473c8ea" xlink:to="loc_swx_BilledOnCompletedContractsAndContractsInProgressMember_ced13c52-94f7-44de-9ee2-6a6641e789e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherReceivablesMember_1bb3b8f4-052d-48c0-9c4b-bfbec27fac4f" xlink:href="swx-20220630.xsd#swx_OtherReceivablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReceivableTypeDomain_6a4b1ce3-3cd5-4b7c-9fee-ec5cc473c8ea" xlink:to="loc_swx_OtherReceivablesMember_1bb3b8f4-052d-48c0-9c4b-bfbec27fac4f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/RevenueScheduleofRegulatedOperationsRevenuesPipelineandStorageSegmentDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#RevenueScheduleofRegulatedOperationsRevenuesPipelineandStorageSegmentDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/RevenueScheduleofRegulatedOperationsRevenuesPipelineandStorageSegmentDetails" xlink:type="extended" id="i686433eeacd345d9b02b68aa827f4e0c_RevenueScheduleofRegulatedOperationsRevenuesPipelineandStorageSegmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_71a481e5-667a-4f9e-9259-18129e81ffae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_f156c202-d44f-406f-ae91-e4f884e7ff07" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_71a481e5-667a-4f9e-9259-18129e81ffae" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_f156c202-d44f-406f-ae91-e4f884e7ff07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherRevenue_4f909326-1578-4585-919a-06800b4986b7" xlink:href="swx-20220630.xsd#swx_OtherRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_71a481e5-667a-4f9e-9259-18129e81ffae" xlink:to="loc_swx_OtherRevenue_4f909326-1578-4585-919a-06800b4986b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RegulatedOperatingRevenueGas_95c385ec-9bc8-4bbf-acc2-32f5c3289b10" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_RegulatedOperatingRevenueGas"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_71a481e5-667a-4f9e-9259-18129e81ffae" xlink:to="loc_us-gaap_RegulatedOperatingRevenueGas_95c385ec-9bc8-4bbf-acc2-32f5c3289b10" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_bcb3637d-71d4-42b5-b50f-6342c55f9885" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_71a481e5-667a-4f9e-9259-18129e81ffae" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_bcb3637d-71d4-42b5-b50f-6342c55f9885" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_5fb3298b-676e-4827-94b8-e672924f6ea0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_bcb3637d-71d4-42b5-b50f-6342c55f9885" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_5fb3298b-676e-4827-94b8-e672924f6ea0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_5fb3298b-676e-4827-94b8-e672924f6ea0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_5fb3298b-676e-4827-94b8-e672924f6ea0" xlink:to="loc_us-gaap_SegmentDomain_5fb3298b-676e-4827-94b8-e672924f6ea0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_148acac0-6e23-4c55-8d30-3d22fb47de9c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_5fb3298b-676e-4827-94b8-e672924f6ea0" xlink:to="loc_us-gaap_SegmentDomain_148acac0-6e23-4c55-8d30-3d22fb47de9c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_PipelineAndStorageSegmentMember_e663e8e5-0eab-432d-b6a9-abcb8e5f3704" xlink:href="swx-20220630.xsd#swx_PipelineAndStorageSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_148acac0-6e23-4c55-8d30-3d22fb47de9c" xlink:to="loc_swx_PipelineAndStorageSegmentMember_e663e8e5-0eab-432d-b6a9-abcb8e5f3704" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_f78ccddd-2275-44ec-bd76-e4f9b2717399" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_bcb3637d-71d4-42b5-b50f-6342c55f9885" xlink:to="loc_srt_ProductOrServiceAxis_f78ccddd-2275-44ec-bd76-e4f9b2717399" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_f78ccddd-2275-44ec-bd76-e4f9b2717399_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_f78ccddd-2275-44ec-bd76-e4f9b2717399" xlink:to="loc_srt_ProductsAndServicesDomain_f78ccddd-2275-44ec-bd76-e4f9b2717399_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_438f5300-f8fd-4683-b22a-e4861fb91a6e" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_f78ccddd-2275-44ec-bd76-e4f9b2717399" xlink:to="loc_srt_ProductsAndServicesDomain_438f5300-f8fd-4683-b22a-e4861fb91a6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RegulatedGasTransportationAndStorageRevenuesMember_8e49a771-ceb4-4186-8254-c80b7189ff65" xlink:href="swx-20220630.xsd#swx_RegulatedGasTransportationAndStorageRevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_438f5300-f8fd-4683-b22a-e4861fb91a6e" xlink:to="loc_swx_RegulatedGasTransportationAndStorageRevenuesMember_8e49a771-ceb4-4186-8254-c80b7189ff65" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_NGLRevenuesMember_f731e6dd-b46f-446b-bbf8-3186d4ffb8ea" xlink:href="swx-20220630.xsd#swx_NGLRevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_438f5300-f8fd-4683-b22a-e4861fb91a6e" xlink:to="loc_swx_NGLRevenuesMember_f731e6dd-b46f-446b-bbf8-3186d4ffb8ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_OtherRevenuesMember_747f48ee-6c14-4754-9593-644f450b33b9" xlink:href="swx-20220630.xsd#swx_OtherRevenuesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_438f5300-f8fd-4683-b22a-e4861fb91a6e" xlink:to="loc_swx_OtherRevenuesMember_747f48ee-6c14-4754-9593-644f450b33b9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/CommonStockNarrativesDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#CommonStockNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/CommonStockNarrativesDetails" xlink:type="extended" id="ia72fb662a8204b62bcdaa8f63b94ff7d_CommonStockNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SaleOfStockAmountOfCommonStockOfferedForSale_f26d2c44-f1cb-49c6-81e7-bcc53b295958" xlink:href="swx-20220630.xsd#swx_SaleOfStockAmountOfCommonStockOfferedForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_swx_SaleOfStockAmountOfCommonStockOfferedForSale_f26d2c44-f1cb-49c6-81e7-bcc53b295958" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SaleOfStockAmountOfCommonStockAvailableForSale_f6bd4389-58ef-4fbe-b774-833de1a9a511" xlink:href="swx-20220630.xsd#swx_SaleOfStockAmountOfCommonStockAvailableForSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_swx_SaleOfStockAmountOfCommonStockAvailableForSale_f6bd4389-58ef-4fbe-b774-833de1a9a511" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_d82de7ee-4ae9-41ea-a200-b720702b11ca" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_d82de7ee-4ae9-41ea-a200-b720702b11ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockPricePerShare_a8868268-5e54-46d0-a7d3-c325524e2cd9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockPricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_us-gaap_SaleOfStockPricePerShare_a8868268-5e54-46d0-a7d3-c325524e2cd9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_d8853b55-4e71-4d3b-b1e8-642bf4c5fe91" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_us-gaap_SaleOfStockConsiderationReceivedOnTransaction_d8853b55-4e71-4d3b-b1e8-642bf4c5fe91" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SaleOfStockUnderwritersDiscount_798cba87-8b56-4d00-af86-4270297cefc3" xlink:href="swx-20220630.xsd#swx_SaleOfStockUnderwritersDiscount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_swx_SaleOfStockUnderwritersDiscount_798cba87-8b56-4d00-af86-4270297cefc3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_a790e7b5-b317-43ea-8563-dd2f074f3efc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_a790e7b5-b317-43ea-8563-dd2f074f3efc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_a70ab9f8-51dd-4f65-969b-540ab48237f3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_a70ab9f8-51dd-4f65-969b-540ab48237f3" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RightsAgreementAmendmentBeneficialOwnershipPercentage_9e6778df-c790-4c16-a29f-6d6eeed1a795" xlink:href="swx-20220630.xsd#swx_RightsAgreementAmendmentBeneficialOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_swx_RightsAgreementAmendmentBeneficialOwnershipPercentage_9e6778df-c790-4c16-a29f-6d6eeed1a795" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_26f15bca-4e02-4455-99b8-b5dae78a0242" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_us-gaap_DebtInstrumentTerm_26f15bca-4e02-4455-99b8-b5dae78a0242" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_14e2ea54-0fe1-411a-86a1-c5c6d97598ee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_5fe33728-5405-46a5-a83d-2336ed60cada" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_14e2ea54-0fe1-411a-86a1-c5c6d97598ee" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_575dce1d-03bc-4a56-b757-ed79b1ee1d34" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_14e2ea54-0fe1-411a-86a1-c5c6d97598ee" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_575dce1d-03bc-4a56-b757-ed79b1ee1d34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_575dce1d-03bc-4a56-b757-ed79b1ee1d34_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_575dce1d-03bc-4a56-b757-ed79b1ee1d34" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_575dce1d-03bc-4a56-b757-ed79b1ee1d34_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f2fe33ac-7427-446b-85ee-9fb4593e5c3a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_575dce1d-03bc-4a56-b757-ed79b1ee1d34" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f2fe33ac-7427-446b-85ee-9fb4593e5c3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_EquityShelfProgramMember_0502cbbd-e0fe-4f63-bfe9-e3c6a8114993" xlink:href="swx-20220630.xsd#swx_EquityShelfProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_f2fe33ac-7427-446b-85ee-9fb4593e5c3a" xlink:to="loc_swx_EquityShelfProgramMember_0502cbbd-e0fe-4f63-bfe9-e3c6a8114993" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_8e0c6cca-3cd5-4466-8d46-66730b8ed70d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_14e2ea54-0fe1-411a-86a1-c5c6d97598ee" xlink:to="loc_us-gaap_PlanNameAxis_8e0c6cca-3cd5-4466-8d46-66730b8ed70d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_8e0c6cca-3cd5-4466-8d46-66730b8ed70d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_8e0c6cca-3cd5-4466-8d46-66730b8ed70d" xlink:to="loc_us-gaap_PlanNameDomain_8e0c6cca-3cd5-4466-8d46-66730b8ed70d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_47778515-8d2f-48ed-bedf-77636143d3e9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_8e0c6cca-3cd5-4466-8d46-66730b8ed70d" xlink:to="loc_us-gaap_PlanNameDomain_47778515-8d2f-48ed-bedf-77636143d3e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RestrictedStockUnitPlanAndManagementIncentivePlanMember_5de6fc32-6f1c-4ef0-8912-49e424959bcc" xlink:href="swx-20220630.xsd#swx_RestrictedStockUnitPlanAndManagementIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_47778515-8d2f-48ed-bedf-77636143d3e9" xlink:to="loc_swx_RestrictedStockUnitPlanAndManagementIncentivePlanMember_5de6fc32-6f1c-4ef0-8912-49e424959bcc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DividendReinvestmentAndStockPurchasePlanMember_c7800185-eb88-4494-b580-98104938d6a4" xlink:href="swx-20220630.xsd#swx_DividendReinvestmentAndStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_47778515-8d2f-48ed-bedf-77636143d3e9" xlink:to="loc_swx_DividendReinvestmentAndStockPurchasePlanMember_c7800185-eb88-4494-b580-98104938d6a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_294b55fc-3b48-4aaf-88ea-d3abc967060c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_14e2ea54-0fe1-411a-86a1-c5c6d97598ee" xlink:to="loc_us-gaap_DebtInstrumentAxis_294b55fc-3b48-4aaf-88ea-d3abc967060c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_294b55fc-3b48-4aaf-88ea-d3abc967060c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_294b55fc-3b48-4aaf-88ea-d3abc967060c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_294b55fc-3b48-4aaf-88ea-d3abc967060c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e89007f9-e21c-4cf5-aff6-bb0c71d88dcd" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_294b55fc-3b48-4aaf-88ea-d3abc967060c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e89007f9-e21c-4cf5-aff6-bb0c71d88dcd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_TermLoanFacilityDueDecember302022Member_5c5f761c-bfc8-4d14-b2d4-4af0d12b6336" xlink:href="swx-20220630.xsd#swx_TermLoanFacilityDueDecember302022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e89007f9-e21c-4cf5-aff6-bb0c71d88dcd" xlink:to="loc_swx_TermLoanFacilityDueDecember302022Member_5c5f761c-bfc8-4d14-b2d4-4af0d12b6336" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_47ab67b1-03c5-4481-861f-572d5fc29929" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_14e2ea54-0fe1-411a-86a1-c5c6d97598ee" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_47ab67b1-03c5-4481-861f-572d5fc29929" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_47ab67b1-03c5-4481-861f-572d5fc29929_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_47ab67b1-03c5-4481-861f-572d5fc29929" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_47ab67b1-03c5-4481-861f-572d5fc29929_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_4f0c0f84-d7d4-4107-b8ae-fe0862fe5e71" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_47ab67b1-03c5-4481-861f-572d5fc29929" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_4f0c0f84-d7d4-4107-b8ae-fe0862fe5e71" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansPayableMember_af37138b-91d8-42af-8dc7-bee9f3c233a7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_4f0c0f84-d7d4-4107-b8ae-fe0862fe5e71" xlink:to="loc_us-gaap_LoansPayableMember_af37138b-91d8-42af-8dc7-bee9f3c233a7" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/CommonStockActivityofEquityShelfProgramDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#CommonStockActivityofEquityShelfProgramDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/CommonStockActivityofEquityShelfProgramDetails" xlink:type="extended" id="i97c3abbe3e64475d879fc5232c1e9de4_CommonStockActivityofEquityShelfProgramDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_3083c578-414e-4b19-9485-e16ddbd02023" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_ProceedsFromIssuanceOfCommonStockGross_034ee13c-d0da-402b-b0b6-cf714e0e8085" xlink:href="swx-20220630.xsd#swx_ProceedsFromIssuanceOfCommonStockGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3083c578-414e-4b19-9485-e16ddbd02023" xlink:to="loc_swx_ProceedsFromIssuanceOfCommonStockGross_034ee13c-d0da-402b-b0b6-cf714e0e8085" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfStockIssuanceCosts_94442e49-fbab-4774-9dcd-7af7df57362e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PaymentsOfStockIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3083c578-414e-4b19-9485-e16ddbd02023" xlink:to="loc_us-gaap_PaymentsOfStockIssuanceCosts_94442e49-fbab-4774-9dcd-7af7df57362e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_5610d350-9daa-4cc3-8596-a4212776c7ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3083c578-414e-4b19-9485-e16ddbd02023" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_5610d350-9daa-4cc3-8596-a4212776c7ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_3f573509-84a8-4b84-8d50-780c272f87a3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3083c578-414e-4b19-9485-e16ddbd02023" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_3f573509-84a8-4b84-8d50-780c272f87a3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CommonStockWeightedAverageIssuePricePerShare_2c147f30-126a-44bb-8abc-62dd35dd36b6" xlink:href="swx-20220630.xsd#swx_CommonStockWeightedAverageIssuePricePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_3083c578-414e-4b19-9485-e16ddbd02023" xlink:to="loc_swx_CommonStockWeightedAverageIssuePricePerShare_2c147f30-126a-44bb-8abc-62dd35dd36b6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_7e1ee842-8ef2-407a-b0ba-cfd3b8b212be" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_3083c578-414e-4b19-9485-e16ddbd02023" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_7e1ee842-8ef2-407a-b0ba-cfd3b8b212be" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_ea2309e8-17cb-46b6-9136-c9244881b96a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SubsidiarySaleOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_7e1ee842-8ef2-407a-b0ba-cfd3b8b212be" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_ea2309e8-17cb-46b6-9136-c9244881b96a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_ea2309e8-17cb-46b6-9136-c9244881b96a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_ea2309e8-17cb-46b6-9136-c9244881b96a" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_ea2309e8-17cb-46b6-9136-c9244881b96a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_452501fb-6204-4886-80ed-28ae57225788" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SaleOfStockNameOfTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_ea2309e8-17cb-46b6-9136-c9244881b96a" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_452501fb-6204-4886-80ed-28ae57225788" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_EquityShelfProgramMember_07be675b-2e9f-4c3f-a643-540a7c694887" xlink:href="swx-20220630.xsd#swx_EquityShelfProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_452501fb-6204-4886-80ed-28ae57225788" xlink:to="loc_swx_EquityShelfProgramMember_07be675b-2e9f-4c3f-a643-540a7c694887" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/DebtScheduleofCarryingAmountsandEstimatedFairValuesofLongTermDebtDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#DebtScheduleofCarryingAmountsandEstimatedFairValuesofLongTermDebtDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/DebtScheduleofCarryingAmountsandEstimatedFairValuesofLongTermDebtDetails" xlink:type="extended" id="ia9b85d43c50c400a88db6791bd0f258f_DebtScheduleofCarryingAmountsandEstimatedFairValuesofLongTermDebtDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_aad6d328-77de-4666-80b1-a3c8d0e81589" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_64c120d6-e1e3-4206-b6bf-bd89333671b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aad6d328-77de-4666-80b1-a3c8d0e81589" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_64c120d6-e1e3-4206-b6bf-bd89333671b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_9a255c7c-7d4e-47f2-8067-9b0140636072" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aad6d328-77de-4666-80b1-a3c8d0e81589" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_9a255c7c-7d4e-47f2-8067-9b0140636072" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_c8c330d5-fcf4-4b06-8d06-878e3162ee75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aad6d328-77de-4666-80b1-a3c8d0e81589" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_c8c330d5-fcf4-4b06-8d06-878e3162ee75" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_5405ba3c-83e7-4f43-bd2a-24fc6f58131f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aad6d328-77de-4666-80b1-a3c8d0e81589" xlink:to="loc_us-gaap_LongTermDebt_5405ba3c-83e7-4f43-bd2a-24fc6f58131f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_bbb94d16-f8a4-489f-896d-baea830402b9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aad6d328-77de-4666-80b1-a3c8d0e81589" xlink:to="loc_us-gaap_LongTermDebtCurrent_bbb94d16-f8a4-489f-896d-baea830402b9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_5c2014bf-a7c7-44c8-a4f6-0a4399c6e49c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aad6d328-77de-4666-80b1-a3c8d0e81589" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_5c2014bf-a7c7-44c8-a4f6-0a4399c6e49c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_3da4da3c-d76a-4eb9-86e0-ed03066144b1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_aad6d328-77de-4666-80b1-a3c8d0e81589" xlink:to="loc_us-gaap_DebtInstrumentTable_3da4da3c-d76a-4eb9-86e0-ed03066144b1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_41154a18-e61f-4057-b7ba-b7d5f6503e75" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3da4da3c-d76a-4eb9-86e0-ed03066144b1" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_41154a18-e61f-4057-b7ba-b7d5f6503e75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_41154a18-e61f-4057-b7ba-b7d5f6503e75_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_41154a18-e61f-4057-b7ba-b7d5f6503e75" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_41154a18-e61f-4057-b7ba-b7d5f6503e75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_aae59703-0bdd-40ec-8506-0a9e8cde24f5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_41154a18-e61f-4057-b7ba-b7d5f6503e75" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_aae59703-0bdd-40ec-8506-0a9e8cde24f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_dbd311d3-ee33-4f6a-8e67-7e16f7aa4d18" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_aae59703-0bdd-40ec-8506-0a9e8cde24f5" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_dbd311d3-ee33-4f6a-8e67-7e16f7aa4d18" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_c3a75c4f-042a-452d-8be6-e5021b6f9a2e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_dbd311d3-ee33-4f6a-8e67-7e16f7aa4d18" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_c3a75c4f-042a-452d-8be6-e5021b6f9a2e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_e3493b8f-96ae-442d-aaa7-4789774c6d4a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_dbd311d3-ee33-4f6a-8e67-7e16f7aa4d18" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_e3493b8f-96ae-442d-aaa7-4789774c6d4a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_38c031e8-566e-44b6-a1ce-51bef94fb1ae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3da4da3c-d76a-4eb9-86e0-ed03066144b1" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_38c031e8-566e-44b6-a1ce-51bef94fb1ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_38c031e8-566e-44b6-a1ce-51bef94fb1ae_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_38c031e8-566e-44b6-a1ce-51bef94fb1ae" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_38c031e8-566e-44b6-a1ce-51bef94fb1ae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_eb00c055-3a7e-4055-9a89-35cb6de7f8de" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_38c031e8-566e-44b6-a1ce-51bef94fb1ae" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_eb00c055-3a7e-4055-9a89-35cb6de7f8de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesMember_6fe2e1bb-5dfb-43f8-9e1a-9f3814ce4f64" xlink:href="swx-20220630.xsd#swx_DebenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_eb00c055-3a7e-4055-9a89-35cb6de7f8de" xlink:to="loc_swx_DebenturesMember_6fe2e1bb-5dfb-43f8-9e1a-9f3814ce4f64" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_RevolvingCreditFacilityAndCommercialPaperMember_0b4cb68c-13f7-4c5b-9df1-0a190dc38d35" xlink:href="swx-20220630.xsd#swx_RevolvingCreditFacilityAndCommercialPaperMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_eb00c055-3a7e-4055-9a89-35cb6de7f8de" xlink:to="loc_swx_RevolvingCreditFacilityAndCommercialPaperMember_0b4cb68c-13f7-4c5b-9df1-0a190dc38d35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_IndustrialDevelopmentRevenueBondsMember_40e92e3c-3a1b-4592-8bdd-e5e31e5f84ae" xlink:href="swx-20220630.xsd#swx_IndustrialDevelopmentRevenueBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_eb00c055-3a7e-4055-9a89-35cb6de7f8de" xlink:to="loc_swx_IndustrialDevelopmentRevenueBondsMember_40e92e3c-3a1b-4592-8bdd-e5e31e5f84ae" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredDebtMember_1434dcca-278e-4f35-9195-32d5871e59e6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_eb00c055-3a7e-4055-9a89-35cb6de7f8de" xlink:to="loc_us-gaap_SecuredDebtMember_1434dcca-278e-4f35-9195-32d5871e59e6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_113e5940-019f-4d9f-a961-5e386ef3cfa1" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_eb00c055-3a7e-4055-9a89-35cb6de7f8de" xlink:to="loc_us-gaap_UnsecuredDebtMember_113e5940-019f-4d9f-a961-5e386ef3cfa1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_8b30609b-5fbf-46e1-87e3-a7e7dd4c5cb9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_eb00c055-3a7e-4055-9a89-35cb6de7f8de" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_8b30609b-5fbf-46e1-87e3-a7e7dd4c5cb9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_59f5b36c-2e4c-452e-a012-3ab2c671c604" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3da4da3c-d76a-4eb9-86e0-ed03066144b1" xlink:to="loc_us-gaap_DebtInstrumentAxis_59f5b36c-2e4c-452e-a012-3ab2c671c604" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_59f5b36c-2e4c-452e-a012-3ab2c671c604_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_59f5b36c-2e4c-452e-a012-3ab2c671c604" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_59f5b36c-2e4c-452e-a012-3ab2c671c604_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_59f5b36c-2e4c-452e-a012-3ab2c671c604" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotes61Due2041Member_c80d2f3c-92a5-4ad6-bba6-ce8fd8eedbf7" xlink:href="swx-20220630.xsd#swx_DebenturesNotes61Due2041Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotes61Due2041Member_c80d2f3c-92a5-4ad6-bba6-ce8fd8eedbf7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesFourPointZeroFivePercentageDueTwoThousandAndThirtyTwoMember_1d86060f-96d6-4a40-8908-ec69558f3857" xlink:href="swx-20220630.xsd#swx_DebenturesNotesFourPointZeroFivePercentageDueTwoThousandAndThirtyTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotesFourPointZeroFivePercentageDueTwoThousandAndThirtyTwoMember_1d86060f-96d6-4a40-8908-ec69558f3857" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesThreePointEightSevenFivePercentageDueTwoThousandAndTwentyTwoMember_0a48e81f-2952-4106-bdcc-3f9da9fee300" xlink:href="swx-20220630.xsd#swx_DebenturesNotesThreePointEightSevenFivePercentageDueTwoThousandAndTwentyTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotesThreePointEightSevenFivePercentageDueTwoThousandAndTwentyTwoMember_0a48e81f-2952-4106-bdcc-3f9da9fee300" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesFourPointEightSevenFivePercentageDueTwoThousandAndFortyThreeMember_05bf593b-e4cd-4a4c-9ae0-61ac19fe63a5" xlink:href="swx-20220630.xsd#swx_DebenturesNotesFourPointEightSevenFivePercentageDueTwoThousandAndFortyThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotesFourPointEightSevenFivePercentageDueTwoThousandAndFortyThreeMember_05bf593b-e4cd-4a4c-9ae0-61ac19fe63a5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesThreePointEightPercentageDueTwoThousandAndFortySixMember_5083f3ef-81b6-406d-8fa5-9761bd2fcc06" xlink:href="swx-20220630.xsd#swx_DebenturesNotesThreePointEightPercentageDueTwoThousandAndFortySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotesThreePointEightPercentageDueTwoThousandAndFortySixMember_5083f3ef-81b6-406d-8fa5-9761bd2fcc06" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesThreePointSevenPercentageDueTwoThousandAndTwentyEightMember_41272067-493a-49bb-8f81-22ab8d3a750b" xlink:href="swx-20220630.xsd#swx_DebenturesNotesThreePointSevenPercentageDueTwoThousandAndTwentyEightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotesThreePointSevenPercentageDueTwoThousandAndTwentyEightMember_41272067-493a-49bb-8f81-22ab8d3a750b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesFourPointFifteenPercentageDueTwoThousandAndFortyNineMember_7a6a5f25-706b-4427-ad93-159e2df621a4" xlink:href="swx-20220630.xsd#swx_DebenturesNotesFourPointFifteenPercentageDueTwoThousandAndFortyNineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotesFourPointFifteenPercentageDueTwoThousandAndFortyNineMember_7a6a5f25-706b-4427-ad93-159e2df621a4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesTwoPointTwoPercentageDueTwoThousandAndThirtyMember_b633a545-58f0-4985-bf4f-d9df95d849d8" xlink:href="swx-20220630.xsd#swx_DebenturesNotesTwoPointTwoPercentageDueTwoThousandAndThirtyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotesTwoPointTwoPercentageDueTwoThousandAndThirtyMember_b633a545-58f0-4985-bf4f-d9df95d849d8" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesThreePointEighteenPercentageDueTwoThousandAndFiftyOneMember_6e1c6848-49ff-4e44-bd39-40631933c419" xlink:href="swx-20220630.xsd#swx_DebenturesNotesThreePointEighteenPercentageDueTwoThousandAndFiftyOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesNotesThreePointEighteenPercentageDueTwoThousandAndFiftyOneMember_6e1c6848-49ff-4e44-bd39-40631933c419" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesEightPercentageSeriesDueTwoThousandAndTwentySixMember_09498805-ec6e-4af2-acaa-396f45feba09" xlink:href="swx-20220630.xsd#swx_DebenturesEightPercentageSeriesDueTwoThousandAndTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesEightPercentageSeriesDueTwoThousandAndTwentySixMember_09498805-ec6e-4af2-acaa-396f45feba09" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesMediumTermNotesSevenPointSevenEightPercentageSeriesDueTwoThousandAndTwentyTwoMember_f24b671d-7a04-4b6a-bdd4-845fb6e4761f" xlink:href="swx-20220630.xsd#swx_DebenturesMediumTermNotesSevenPointSevenEightPercentageSeriesDueTwoThousandAndTwentyTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesMediumTermNotesSevenPointSevenEightPercentageSeriesDueTwoThousandAndTwentyTwoMember_f24b671d-7a04-4b6a-bdd4-845fb6e4761f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesMediumTermNotesSevenPointNineTwoPercentageSeriesDueTwoThousandAndTwentySevenMember_d5aebdc3-9a7f-4ec1-83ff-0221d2b2cf10" xlink:href="swx-20220630.xsd#swx_DebenturesMediumTermNotesSevenPointNineTwoPercentageSeriesDueTwoThousandAndTwentySevenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesMediumTermNotesSevenPointNineTwoPercentageSeriesDueTwoThousandAndTwentySevenMember_d5aebdc3-9a7f-4ec1-83ff-0221d2b2cf10" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesMediumTermNotesSixPointSevenSixPercentageSeriesDueTwoThousandAndTwentySevenMember_3a5eb2d0-1f65-4e2b-973a-74451b0ddc0a" xlink:href="swx-20220630.xsd#swx_DebenturesMediumTermNotesSixPointSevenSixPercentageSeriesDueTwoThousandAndTwentySevenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_DebenturesMediumTermNotesSixPointSevenSixPercentageSeriesDueTwoThousandAndTwentySevenMember_3a5eb2d0-1f65-4e2b-973a-74451b0ddc0a" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_VariableRateBondsTaxExemptSeriesADueTwoThousandAndTwentyEightMember_b6fcf70d-aa4d-4858-bb3f-b12e1101d9d0" xlink:href="swx-20220630.xsd#swx_VariableRateBondsTaxExemptSeriesADueTwoThousandAndTwentyEightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_VariableRateBondsTaxExemptSeriesADueTwoThousandAndTwentyEightMember_b6fcf70d-aa4d-4858-bb3f-b12e1101d9d0" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_VariableRateBondsTwoThousandAndThreeSeriesADueTwoThousandAndThirtyEightMember_caea97c7-dfb7-4f16-ae41-7b709ede9e26" xlink:href="swx-20220630.xsd#swx_VariableRateBondsTwoThousandAndThreeSeriesADueTwoThousandAndThirtyEightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_VariableRateBondsTwoThousandAndThreeSeriesADueTwoThousandAndThirtyEightMember_caea97c7-dfb7-4f16-ae41-7b709ede9e26" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_VariableRateBondsTwoThousandAndEightSeriesADueTwoThousandAndThirtyEightMember_258bc97a-fe53-414d-b18c-ae856be1f8b0" xlink:href="swx-20220630.xsd#swx_VariableRateBondsTwoThousandAndEightSeriesADueTwoThousandAndThirtyEightMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_VariableRateBondsTwoThousandAndEightSeriesADueTwoThousandAndThirtyEightMember_258bc97a-fe53-414d-b18c-ae856be1f8b0" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_VariableRateBondsTwoThousandAndNineSeriesADueTwoThousandAndThirtyNineMember_d7986c3c-dd11-4661-b4ab-26ceb5876924" xlink:href="swx-20220630.xsd#swx_VariableRateBondsTwoThousandAndNineSeriesADueTwoThousandAndThirtyNineMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_VariableRateBondsTwoThousandAndNineSeriesADueTwoThousandAndThirtyNineMember_d7986c3c-dd11-4661-b4ab-26ceb5876924" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiSecuredTermLoanFacilityMember_58526f01-8819-4ba6-b099-d43fdbfd173c" xlink:href="swx-20220630.xsd#swx_CenturiSecuredTermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_CenturiSecuredTermLoanFacilityMember_58526f01-8819-4ba6-b099-d43fdbfd173c" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SeniorNotes353DueIn2028Member_f20dd3f4-7701-44e9-8aa1-2e60346bac24" xlink:href="swx-20220630.xsd#swx_SeniorNotes353DueIn2028Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_SeniorNotes353DueIn2028Member_f20dd3f4-7701-44e9-8aa1-2e60346bac24" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SeniorNotes4875DueIn2041Member_c3a5ab64-dc59-4d1b-a4d8-40e54f834e14" xlink:href="swx-20220630.xsd#swx_SeniorNotes4875DueIn2041Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_SeniorNotes4875DueIn2041Member_c3a5ab64-dc59-4d1b-a4d8-40e54f834e14" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SeniorNotes391DueIn2038Member_b2114996-a3f1-4257-b4b1-db5c407b1027" xlink:href="swx-20220630.xsd#swx_SeniorNotes391DueIn2038Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_dd3d9154-eaaa-4c26-ab66-dcce82408049" xlink:to="loc_swx_SeniorNotes391DueIn2038Member_b2114996-a3f1-4257-b4b1-db5c407b1027" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_65e69f78-4aaa-41d5-a4b7-06b896794cf4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3da4da3c-d76a-4eb9-86e0-ed03066144b1" xlink:to="loc_us-gaap_CreditFacilityAxis_65e69f78-4aaa-41d5-a4b7-06b896794cf4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_65e69f78-4aaa-41d5-a4b7-06b896794cf4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_65e69f78-4aaa-41d5-a4b7-06b896794cf4" xlink:to="loc_us-gaap_CreditFacilityDomain_65e69f78-4aaa-41d5-a4b7-06b896794cf4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_98786f59-89b3-424b-a4c7-1c34959e669b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_65e69f78-4aaa-41d5-a4b7-06b896794cf4" xlink:to="loc_us-gaap_CreditFacilityDomain_98786f59-89b3-424b-a4c7-1c34959e669b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiSecuredRevolvingCreditFacilityMember_f117a535-bd41-45ce-af62-247698d38505" xlink:href="swx-20220630.xsd#swx_CenturiSecuredRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_98786f59-89b3-424b-a4c7-1c34959e669b" xlink:to="loc_swx_CenturiSecuredRevolvingCreditFacilityMember_f117a535-bd41-45ce-af62-247698d38505" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_bae61e7b-5c46-4f0a-9c16-ddaff311b9a4" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3da4da3c-d76a-4eb9-86e0-ed03066144b1" xlink:to="loc_dei_LegalEntityAxis_bae61e7b-5c46-4f0a-9c16-ddaff311b9a4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_bae61e7b-5c46-4f0a-9c16-ddaff311b9a4_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_bae61e7b-5c46-4f0a-9c16-ddaff311b9a4" xlink:to="loc_dei_EntityDomain_bae61e7b-5c46-4f0a-9c16-ddaff311b9a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_aaf80ec8-ac1e-490f-a1c3-0c4a808b8370" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_bae61e7b-5c46-4f0a-9c16-ddaff311b9a4" xlink:to="loc_dei_EntityDomain_aaf80ec8-ac1e-490f-a1c3-0c4a808b8370" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_c722bfcf-16d1-433f-b17e-913a414595a4" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_aaf80ec8-ac1e-490f-a1c3-0c4a808b8370" xlink:to="loc_swx_SouthwestGasCorporationMember_c722bfcf-16d1-433f-b17e-913a414595a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiGroupInc.Member_607e8027-f5db-482c-acc0-5a6cd7bb25ec" xlink:href="swx-20220630.xsd#swx_CenturiGroupInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_aaf80ec8-ac1e-490f-a1c3-0c4a808b8370" xlink:to="loc_swx_CenturiGroupInc.Member_607e8027-f5db-482c-acc0-5a6cd7bb25ec" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/DebtNarrativesDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#DebtNarrativesDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/DebtNarrativesDetails" xlink:type="extended" id="i7a3399e0c1c14f1fa4ab182d164ea2c8_DebtNarrativesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_2dacc875-9fe8-4d84-9031-069e3fc4ef71" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_2dacc875-9fe8-4d84-9031-069e3fc4ef71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LineOfCreditFacilityAmountClassifiedAsLongTermDebt_b6c63262-fd48-41e1-9538-206a766ce7d4" xlink:href="swx-20220630.xsd#swx_LineOfCreditFacilityAmountClassifiedAsLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_swx_LineOfCreditFacilityAmountClassifiedAsLongTermDebt_b6c63262-fd48-41e1-9538-206a766ce7d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_LineOfCreditFacilityWorkingCapitalPurposes_870233bb-6d6f-43a8-a1f3-cc4413052201" xlink:href="swx-20220630.xsd#swx_LineOfCreditFacilityWorkingCapitalPurposes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_swx_LineOfCreditFacilityWorkingCapitalPurposes_870233bb-6d6f-43a8-a1f3-cc4413052201" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_462f88e2-0788-4258-9046-1300b95cbe69" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_462f88e2-0788-4258-9046-1300b95cbe69" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_bc4b1705-f822-48e1-ace5-2ff062038f12" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_LongTermDebt_bc4b1705-f822-48e1-ace5-2ff062038f12" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_b16bdd6c-630b-432f-bc63-238678673e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_LineOfCredit_b16bdd6c-630b-432f-bc63-238678673e4d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_ee81900a-4127-4d4c-8fcf-648e4b97f160" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_ee81900a-4127-4d4c-8fcf-648e4b97f160" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_8ab3912d-e251-44ad-b6b6-f7973ed175ec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_8ab3912d-e251-44ad-b6b6-f7973ed175ec" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebtInstrumentDiscountRate_b2f333c0-4624-4178-a60c-4d1d3eb010a5" xlink:href="swx-20220630.xsd#swx_DebtInstrumentDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_swx_DebtInstrumentDiscountRate_b2f333c0-4624-4178-a60c-4d1d3eb010a5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCollateralAmount_f279fce4-e8d9-4ae2-918d-8303b26df54d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCollateralAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_DebtInstrumentCollateralAmount_f279fce4-e8d9-4ae2-918d-8303b26df54d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebtInstrumentNumberOfPrivatePlacementUnsecuredSeniorNotes_07a09983-f308-4cc4-94dc-88bdd65da919" xlink:href="swx-20220630.xsd#swx_DebtInstrumentNumberOfPrivatePlacementUnsecuredSeniorNotes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_swx_DebtInstrumentNumberOfPrivatePlacementUnsecuredSeniorNotes_07a09983-f308-4cc4-94dc-88bdd65da919" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_cf99a282-23e7-4fbe-b22e-74b14df97c78" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_cf99a282-23e7-4fbe-b22e-74b14df97c78" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermBorrowings_56ab2538-1b6e-4f3d-b649-cbe6e64351a0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_ShortTermBorrowings_56ab2538-1b6e-4f3d-b649-cbe6e64351a0" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_7641e558-4ebc-4ac3-ad52-46f9d76c319a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_DebtInstrumentTerm_7641e558-4ebc-4ac3-ad52-46f9d76c319a" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_NegativeWorkingCapitalCondition_3b01ab03-f3fd-4a3a-aff1-6706b69ed578" xlink:href="swx-20220630.xsd#swx_NegativeWorkingCapitalCondition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_swx_NegativeWorkingCapitalCondition_3b01ab03-f3fd-4a3a-aff1-6706b69ed578" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_52c1c0a6-c049-4dee-bd69-653dda3354b8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_0bbebf35-7e0b-407d-80b8-e8ae9975c1d7" xlink:to="loc_us-gaap_DebtInstrumentTable_52c1c0a6-c049-4dee-bd69-653dda3354b8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_11e598cb-2881-4bf5-9069-75a1ae2da718" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_52c1c0a6-c049-4dee-bd69-653dda3354b8" xlink:to="loc_us-gaap_CreditFacilityAxis_11e598cb-2881-4bf5-9069-75a1ae2da718" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_11e598cb-2881-4bf5-9069-75a1ae2da718_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_11e598cb-2881-4bf5-9069-75a1ae2da718" xlink:to="loc_us-gaap_CreditFacilityDomain_11e598cb-2881-4bf5-9069-75a1ae2da718_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_51a23830-8e77-4fda-a184-9bfc970d7b29" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_11e598cb-2881-4bf5-9069-75a1ae2da718" xlink:to="loc_us-gaap_CreditFacilityDomain_51a23830-8e77-4fda-a184-9bfc970d7b29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_A400MillionCreditFacilityMember_1a6c8619-00d2-48b2-8b6e-8b5c652cba21" xlink:href="swx-20220630.xsd#swx_A400MillionCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_51a23830-8e77-4fda-a184-9bfc970d7b29" xlink:to="loc_swx_A400MillionCreditFacilityMember_1a6c8619-00d2-48b2-8b6e-8b5c652cba21" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CommercialPaperProgramMember_e7e0d868-cbfd-4b07-affc-9b67fad4fb16" xlink:href="swx-20220630.xsd#swx_CommercialPaperProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_51a23830-8e77-4fda-a184-9bfc970d7b29" xlink:to="loc_swx_CommercialPaperProgramMember_e7e0d868-cbfd-4b07-affc-9b67fad4fb16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiSecuredRevolvingCreditFacilityMember_f4f57db9-b51b-4c55-9064-30cc94f11152" xlink:href="swx-20220630.xsd#swx_CenturiSecuredRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_51a23830-8e77-4fda-a184-9bfc970d7b29" xlink:to="loc_swx_CenturiSecuredRevolvingCreditFacilityMember_f4f57db9-b51b-4c55-9064-30cc94f11152" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_A100MillionCreditFacilityMember_69980192-6c02-4b04-8a53-bd7fef75fa11" xlink:href="swx-20220630.xsd#swx_A100MillionCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_51a23830-8e77-4fda-a184-9bfc970d7b29" xlink:to="loc_swx_A100MillionCreditFacilityMember_69980192-6c02-4b04-8a53-bd7fef75fa11" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_3ae0c068-34c7-4ad9-a0f3-924bdc37c522" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_52c1c0a6-c049-4dee-bd69-653dda3354b8" xlink:to="loc_dei_LegalEntityAxis_3ae0c068-34c7-4ad9-a0f3-924bdc37c522" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_3ae0c068-34c7-4ad9-a0f3-924bdc37c522_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_3ae0c068-34c7-4ad9-a0f3-924bdc37c522" xlink:to="loc_dei_EntityDomain_3ae0c068-34c7-4ad9-a0f3-924bdc37c522_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_06069954-5249-402b-82a2-158fd3ee3841" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_3ae0c068-34c7-4ad9-a0f3-924bdc37c522" xlink:to="loc_dei_EntityDomain_06069954-5249-402b-82a2-158fd3ee3841" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_725c6a1a-4ca8-4e39-b1da-e8a30cdb47f1" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_06069954-5249-402b-82a2-158fd3ee3841" xlink:to="loc_swx_SouthwestGasCorporationMember_725c6a1a-4ca8-4e39-b1da-e8a30cdb47f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiGroupInc.Member_392da02d-ce38-4dd4-8195-5bab82974702" xlink:href="swx-20220630.xsd#swx_CenturiGroupInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_06069954-5249-402b-82a2-158fd3ee3841" xlink:to="loc_swx_CenturiGroupInc.Member_392da02d-ce38-4dd4-8195-5bab82974702" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_MountainWestMember_7ace2b49-434b-4874-b4de-1bfc2e06f921" xlink:href="swx-20220630.xsd#swx_MountainWestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_06069954-5249-402b-82a2-158fd3ee3841" xlink:to="loc_swx_MountainWestMember_7ace2b49-434b-4874-b4de-1bfc2e06f921" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_0a8c4a3d-d53b-472f-920d-70b1864fc3eb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_52c1c0a6-c049-4dee-bd69-653dda3354b8" xlink:to="loc_us-gaap_VariableRateAxis_0a8c4a3d-d53b-472f-920d-70b1864fc3eb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_0a8c4a3d-d53b-472f-920d-70b1864fc3eb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_0a8c4a3d-d53b-472f-920d-70b1864fc3eb" xlink:to="loc_us-gaap_VariableRateDomain_0a8c4a3d-d53b-472f-920d-70b1864fc3eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_de986c45-5ac7-46bd-a3cb-43d0c0cf73c0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_0a8c4a3d-d53b-472f-920d-70b1864fc3eb" xlink:to="loc_us-gaap_VariableRateDomain_de986c45-5ac7-46bd-a3cb-43d0c0cf73c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_bf846c27-235a-4db1-a975-8dfbfe09f3ee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_de986c45-5ac7-46bd-a3cb-43d0c0cf73c0" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_bf846c27-235a-4db1-a975-8dfbfe09f3ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BaseRateMember_25eac75e-ef00-4529-831b-2f8c91716660" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_de986c45-5ac7-46bd-a3cb-43d0c0cf73c0" xlink:to="loc_us-gaap_BaseRateMember_25eac75e-ef00-4529-831b-2f8c91716660" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_5f6b86a4-7171-4b78-86bd-525fec755245" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_de986c45-5ac7-46bd-a3cb-43d0c0cf73c0" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_5f6b86a4-7171-4b78-86bd-525fec755245" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_33dbd604-91ef-4030-8494-2428ae1f3dc0" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_52c1c0a6-c049-4dee-bd69-653dda3354b8" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_33dbd604-91ef-4030-8494-2428ae1f3dc0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_33dbd604-91ef-4030-8494-2428ae1f3dc0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_33dbd604-91ef-4030-8494-2428ae1f3dc0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_33dbd604-91ef-4030-8494-2428ae1f3dc0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_c5afb0c3-1f24-4bb8-8fd0-69ba9fdeaca6" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_33dbd604-91ef-4030-8494-2428ae1f3dc0" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_c5afb0c3-1f24-4bb8-8fd0-69ba9fdeaca6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesMember_1a1f7210-4b0d-409a-8089-fce2f5a3468c" xlink:href="swx-20220630.xsd#swx_DebenturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c5afb0c3-1f24-4bb8-8fd0-69ba9fdeaca6" xlink:to="loc_swx_DebenturesMember_1a1f7210-4b0d-409a-8089-fce2f5a3468c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_e1bb8564-c453-42ce-9861-9fc7470c6d5d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c5afb0c3-1f24-4bb8-8fd0-69ba9fdeaca6" xlink:to="loc_us-gaap_LineOfCreditMember_e1bb8564-c453-42ce-9861-9fc7470c6d5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_4dfa3562-d0b6-4d4c-a32a-1490741e13db" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_c5afb0c3-1f24-4bb8-8fd0-69ba9fdeaca6" xlink:to="loc_us-gaap_UnsecuredDebtMember_4dfa3562-d0b6-4d4c-a32a-1490741e13db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_cc2bc153-052e-4106-a02c-c93c361a1b4a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_52c1c0a6-c049-4dee-bd69-653dda3354b8" xlink:to="loc_us-gaap_DebtInstrumentAxis_cc2bc153-052e-4106-a02c-c93c361a1b4a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_cc2bc153-052e-4106-a02c-c93c361a1b4a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_cc2bc153-052e-4106-a02c-c93c361a1b4a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_cc2bc153-052e-4106-a02c-c93c361a1b4a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_378f002f-d693-4503-8fff-3af55064cb30" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_cc2bc153-052e-4106-a02c-c93c361a1b4a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_378f002f-d693-4503-8fff-3af55064cb30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesFourPointZeroFivePercentageDueTwoThousandAndThirtyTwoMember_64cb6df8-bcdc-49ce-b3fb-0dc05a01a09d" xlink:href="swx-20220630.xsd#swx_DebenturesNotesFourPointZeroFivePercentageDueTwoThousandAndThirtyTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_378f002f-d693-4503-8fff-3af55064cb30" xlink:to="loc_swx_DebenturesNotesFourPointZeroFivePercentageDueTwoThousandAndThirtyTwoMember_64cb6df8-bcdc-49ce-b3fb-0dc05a01a09d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DebenturesNotesThreePointEightSevenFivePercentageDueTwoThousandAndTwentyTwoMember_701f45ed-807d-43d8-b5f1-39399d93bb47" xlink:href="swx-20220630.xsd#swx_DebenturesNotesThreePointEightSevenFivePercentageDueTwoThousandAndTwentyTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_378f002f-d693-4503-8fff-3af55064cb30" xlink:to="loc_swx_DebenturesNotesThreePointEightSevenFivePercentageDueTwoThousandAndTwentyTwoMember_701f45ed-807d-43d8-b5f1-39399d93bb47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiTermLoanFacilityMember_f1659380-06fd-43b2-98d1-48631a20b242" xlink:href="swx-20220630.xsd#swx_CenturiTermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_378f002f-d693-4503-8fff-3af55064cb30" xlink:to="loc_swx_CenturiTermLoanFacilityMember_f1659380-06fd-43b2-98d1-48631a20b242" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiSecuredTermLoanFacilityAndRevolvingCreditFacilityMember_391cc575-10fc-402d-8292-30b3b6557b17" xlink:href="swx-20220630.xsd#swx_CenturiSecuredTermLoanFacilityAndRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_378f002f-d693-4503-8fff-3af55064cb30" xlink:to="loc_swx_CenturiSecuredTermLoanFacilityAndRevolvingCreditFacilityMember_391cc575-10fc-402d-8292-30b3b6557b17" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_March2021TermLoanMember_a047cb7b-ee0b-4891-994a-5bf50bc5f602" xlink:href="swx-20220630.xsd#swx_March2021TermLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_378f002f-d693-4503-8fff-3af55064cb30" xlink:to="loc_swx_March2021TermLoanMember_a047cb7b-ee0b-4891-994a-5bf50bc5f602" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_TermLoanFacilityDueDecember302022Member_0b8f22b7-438f-437f-a035-75e94304834f" xlink:href="swx-20220630.xsd#swx_TermLoanFacilityDueDecember302022Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_378f002f-d693-4503-8fff-3af55064cb30" xlink:to="loc_swx_TermLoanFacilityDueDecember302022Member_0b8f22b7-438f-437f-a035-75e94304834f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeAxis_2aaaf883-76cd-46e2-a38a-5e929670993c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_52c1c0a6-c049-4dee-bd69-653dda3354b8" xlink:to="loc_us-gaap_ShortTermDebtTypeAxis_2aaaf883-76cd-46e2-a38a-5e929670993c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_2aaaf883-76cd-46e2-a38a-5e929670993c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_2aaaf883-76cd-46e2-a38a-5e929670993c" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_2aaaf883-76cd-46e2-a38a-5e929670993c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermDebtTypeDomain_ed460d6e-d7a3-4cfa-8de6-694582dc81aa" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ShortTermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShortTermDebtTypeAxis_2aaaf883-76cd-46e2-a38a-5e929670993c" xlink:to="loc_us-gaap_ShortTermDebtTypeDomain_ed460d6e-d7a3-4cfa-8de6-694582dc81aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansPayableMember_67397d1e-ec6a-49e3-92bd-786ab9d33503" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_LoansPayableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShortTermDebtTypeDomain_ed460d6e-d7a3-4cfa-8de6-694582dc81aa" xlink:to="loc_us-gaap_LoansPayableMember_67397d1e-ec6a-49e3-92bd-786ab9d33503" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/OtherComprehensiveIncomeandAccumulatedOtherComprehensiveIncomeRelatedTaxEffectsAllocatedtoOCIDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#OtherComprehensiveIncomeandAccumulatedOtherComprehensiveIncomeRelatedTaxEffectsAllocatedtoOCIDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/OtherComprehensiveIncomeandAccumulatedOtherComprehensiveIncomeRelatedTaxEffectsAllocatedtoOCIDetails" xlink:type="extended" id="i0862cfcdd8f24ce6ad09e2f140d196ce_OtherComprehensiveIncomeandAccumulatedOtherComprehensiveIncomeRelatedTaxEffectsAllocatedtoOCIDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_8b11f0a1-476a-40e6-a427-001dd2030e3b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_8b11f0a1-476a-40e6-a427-001dd2030e3b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_8a749863-eda1-416e-bf5c-f1c5a1cd1fa4" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_8a749863-eda1-416e-bf5c-f1c5a1cd1fa4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_8e7379ba-2ba3-4c01-81c7-272c43f052dc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_8e7379ba-2ba3-4c01-81c7-272c43f052dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_6f11602a-70d5-4df1-8216-b82cb5e1480c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_6f11602a-70d5-4df1-8216-b82cb5e1480c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_7f32b514-da87-4d5a-9408-efcd8d00fa82" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_7f32b514-da87-4d5a-9408-efcd8d00fa82" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_0a2f6662-53f4-4395-9b74-fad490a1561f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_0a2f6662-53f4-4395-9b74-fad490a1561f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_61c2c271-baea-4d17-b2f5-d4af8cfc0bc8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_61c2c271-baea-4d17-b2f5-d4af8cfc0bc8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_484b834e-44a9-4e9a-a760-0121f11a956c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsTax_484b834e-44a9-4e9a-a760-0121f11a956c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_919532ec-5ad9-4bad-abfa-566750c20c6a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_919532ec-5ad9-4bad-abfa-566750c20c6a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_30e77065-1438-4f1d-bc6d-07ace4b6dcdc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_30e77065-1438-4f1d-bc6d-07ace4b6dcdc" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_3558f627-11eb-40d0-b9ec-c611e64e50e2" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_9c0adb4f-dd0d-4301-a06b-5cfc4328204c" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_3558f627-11eb-40d0-b9ec-c611e64e50e2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_9d977e9a-acc3-49c5-b265-df4fcc970f45" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_3558f627-11eb-40d0-b9ec-c611e64e50e2" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_9d977e9a-acc3-49c5-b265-df4fcc970f45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9d977e9a-acc3-49c5-b265-df4fcc970f45_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9d977e9a-acc3-49c5-b265-df4fcc970f45" xlink:to="loc_us-gaap_EquityComponentDomain_9d977e9a-acc3-49c5-b265-df4fcc970f45_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_1c037485-f915-42e7-8330-4745c69224b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9d977e9a-acc3-49c5-b265-df4fcc970f45" xlink:to="loc_us-gaap_EquityComponentDomain_1c037485-f915-42e7-8330-4745c69224b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_4d0c5520-083f-4931-b9e8-2478e51bd41a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1c037485-f915-42e7-8330-4745c69224b7" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_4d0c5520-083f-4931-b9e8-2478e51bd41a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_e45c73d0-936d-44c3-929e-0d64ac267737" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_4d0c5520-083f-4931-b9e8-2478e51bd41a" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_e45c73d0-936d-44c3-929e-0d64ac267737" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_bef2be3c-be57-4bb9-a443-4e5b6c80f206" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_4d0c5520-083f-4931-b9e8-2478e51bd41a" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_bef2be3c-be57-4bb9-a443-4e5b6c80f206" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_AccumulatedDefinedBenefitPlansAdjustmentRegulartoryAdjustmentAttributabletoParentMember_6a5927cb-dd36-4dc6-903c-10586c1869f4" xlink:href="swx-20220630.xsd#swx_AccumulatedDefinedBenefitPlansAdjustmentRegulartoryAdjustmentAttributabletoParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_4d0c5520-083f-4931-b9e8-2478e51bd41a" xlink:to="loc_swx_AccumulatedDefinedBenefitPlansAdjustmentRegulartoryAdjustmentAttributabletoParentMember_6a5927cb-dd36-4dc6-903c-10586c1869f4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociDerivativeQualifyingAsHedgeExcludedComponentParentMember_a2ad6533-284f-4dbc-9260-d57a93e26cc8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AociDerivativeQualifyingAsHedgeExcludedComponentParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1c037485-f915-42e7-8330-4745c69224b7" xlink:to="loc_us-gaap_AociDerivativeQualifyingAsHedgeExcludedComponentParentMember_a2ad6533-284f-4dbc-9260-d57a93e26cc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_1c13738e-a631-4574-b202-9cae5b77cb43" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_1c037485-f915-42e7-8330-4745c69224b7" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_1c13738e-a631-4574-b202-9cae5b77cb43" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_5d42bf46-26fb-4980-901f-2e8723af9d86" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_3558f627-11eb-40d0-b9ec-c611e64e50e2" xlink:to="loc_dei_LegalEntityAxis_5d42bf46-26fb-4980-901f-2e8723af9d86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_5d42bf46-26fb-4980-901f-2e8723af9d86_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_5d42bf46-26fb-4980-901f-2e8723af9d86" xlink:to="loc_dei_EntityDomain_5d42bf46-26fb-4980-901f-2e8723af9d86_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_4f029bad-d11f-4b01-8312-5efa359fc664" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_5d42bf46-26fb-4980-901f-2e8723af9d86" xlink:to="loc_dei_EntityDomain_4f029bad-d11f-4b01-8312-5efa359fc664" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_f279601f-1401-401b-a91c-91ec01c1317a" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_4f029bad-d11f-4b01-8312-5efa359fc664" xlink:to="loc_swx_SouthwestGasCorporationMember_f279601f-1401-401b-a91c-91ec01c1317a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/OtherComprehensiveIncomeandAccumulatedOtherComprehensiveIncomeAOCIRollforwardDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#OtherComprehensiveIncomeandAccumulatedOtherComprehensiveIncomeAOCIRollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/OtherComprehensiveIncomeandAccumulatedOtherComprehensiveIncomeAOCIRollforwardDetails" xlink:type="extended" id="i2527436816b74809b9dc88cf69278190_OtherComprehensiveIncomeandAccumulatedOtherComprehensiveIncomeAOCIRollforwardDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4a1bc90e-3ee7-47c3-be2d-87ebebb6b371" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4a1bc90e-3ee7-47c3-be2d-87ebebb6b371" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestBeforeTax_fafb5397-2fec-4083-abaf-0731937c129a" xlink:href="swx-20220630.xsd#swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestBeforeTax_fafb5397-2fec-4083-abaf-0731937c129a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestTax_ac6488ef-df9e-4038-babb-9c1d4f814e6d" xlink:href="swx-20220630.xsd#swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestTax_ac6488ef-df9e-4038-babb-9c1d4f814e6d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_f48336a7-df79-4eeb-b636-8004c96f8206" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_f48336a7-df79-4eeb-b636-8004c96f8206" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_StockholdersEquityAttributableToParentBeforeTax_412f350a-c59b-4ea9-bed9-5f74d00e7fa0" xlink:href="swx-20220630.xsd#swx_StockholdersEquityAttributableToParentBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_swx_StockholdersEquityAttributableToParentBeforeTax_412f350a-c59b-4ea9-bed9-5f74d00e7fa0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_StockholdersEquityAttributableToParentTax_36693a46-7be6-4510-91eb-d9d6535a93f2" xlink:href="swx-20220630.xsd#swx_StockholdersEquityAttributableToParentTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_swx_StockholdersEquityAttributableToParentTax_36693a46-7be6-4510-91eb-d9d6535a93f2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_7ff6bf45-c250-4c97-b77c-8f4807105b68" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_StockholdersEquity_7ff6bf45-c250-4c97-b77c-8f4807105b68" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_eae019f2-0ca3-46f1-995a-48626347160a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsBeforeTax_eae019f2-0ca3-46f1-995a-48626347160a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_82823e8d-e7d1-4228-a0c6-f50476f9522a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_82823e8d-e7d1-4228-a0c6-f50476f9522a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_d0db2af6-998d-43df-b296-3069ce16dd92" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodBeforeTax_d0db2af6-998d-43df-b296-3069ce16dd92" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_632daf6a-7108-4990-bd42-062587db4f88" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAociCurrentPeriodTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_ReclassificationFromAociCurrentPeriodTax_632daf6a-7108-4990-bd42-062587db4f88" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_92a0bafc-a956-4c60-ade6-5d3ef063b876" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_92a0bafc-a956-4c60-ade6-5d3ef063b876" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_15c30e16-d9b2-4923-bc15-d7dbc6fac21d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_15c30e16-d9b2-4923-bc15-d7dbc6fac21d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossTax_21fb1c2a-4294-4422-b399-847dbfe9b6b8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossTax_21fb1c2a-4294-4422-b399-847dbfe9b6b8" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_472786ae-715f-4830-ad13-0b3d9bc60e27" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_d55dbc48-2854-453e-b3a4-6ff8776d01df" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_472786ae-715f-4830-ad13-0b3d9bc60e27" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestBeforeTax_d8947979-2152-497d-89b7-242f37f89c7f" xlink:href="swx-20220630.xsd#swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestBeforeTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestTax_ea247d10-52f1-41d5-bed1-793ddbee1dda" xlink:href="swx-20220630.xsd#swx_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_656bab40-8a87-4112-bf8b-1bccd47fa837" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_StockholdersEquityAttributableToParentBeforeTax_b68cddf4-1cbd-453c-b2ff-eb041a7b8127" xlink:href="swx-20220630.xsd#swx_StockholdersEquityAttributableToParentBeforeTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_StockholdersEquityAttributableToParentTax_46ba52c5-f41d-4c0d-8e66-b9c150c2ca5f" xlink:href="swx-20220630.xsd#swx_StockholdersEquityAttributableToParentTax"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_83bb83b2-02f8-4db2-986a-e6b798cd2337" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_3ecdfa27-436e-4d87-9ea4-19c12c480604" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4a1bc90e-3ee7-47c3-be2d-87ebebb6b371" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_3ecdfa27-436e-4d87-9ea4-19c12c480604" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_23bbf059-6042-45a9-9a67-c86dfb900c51" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4a1bc90e-3ee7-47c3-be2d-87ebebb6b371" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_23bbf059-6042-45a9-9a67-c86dfb900c51" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_095475af-939b-43b0-8775-d21a2a6e7cee" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_23bbf059-6042-45a9-9a67-c86dfb900c51" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_095475af-939b-43b0-8775-d21a2a6e7cee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_095475af-939b-43b0-8775-d21a2a6e7cee_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_095475af-939b-43b0-8775-d21a2a6e7cee" xlink:to="loc_us-gaap_EquityComponentDomain_095475af-939b-43b0-8775-d21a2a6e7cee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ffa82a25-d7f4-4d53-95e1-ac183aa07165" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_095475af-939b-43b0-8775-d21a2a6e7cee" xlink:to="loc_us-gaap_EquityComponentDomain_ffa82a25-d7f4-4d53-95e1-ac183aa07165" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_6b059b4c-62e6-49ac-abf0-1731f0513cff" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ffa82a25-d7f4-4d53-95e1-ac183aa07165" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_6b059b4c-62e6-49ac-abf0-1731f0513cff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_fe795d01-3b88-4d5a-bb4f-036f56b11662" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_6b059b4c-62e6-49ac-abf0-1731f0513cff" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetPriorServiceCostCreditMember_fe795d01-3b88-4d5a-bb4f-036f56b11662" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_21a73264-3e5e-4f2c-9056-69d4c920741c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_6b059b4c-62e6-49ac-abf0-1731f0513cff" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentNetUnamortizedGainLossMember_21a73264-3e5e-4f2c-9056-69d4c920741c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_AccumulatedDefinedBenefitPlansAdjustmentRegulartoryAdjustmentAttributabletoParentMember_782f21d2-a32a-41f2-8f53-485cbd919e5e" xlink:href="swx-20220630.xsd#swx_AccumulatedDefinedBenefitPlansAdjustmentRegulartoryAdjustmentAttributabletoParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_6b059b4c-62e6-49ac-abf0-1731f0513cff" xlink:to="loc_swx_AccumulatedDefinedBenefitPlansAdjustmentRegulartoryAdjustmentAttributabletoParentMember_782f21d2-a32a-41f2-8f53-485cbd919e5e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociDerivativeQualifyingAsHedgeExcludedComponentParentMember_923f71ca-e448-45f3-a153-b651ad3d4a86" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AociDerivativeQualifyingAsHedgeExcludedComponentParentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ffa82a25-d7f4-4d53-95e1-ac183aa07165" xlink:to="loc_us-gaap_AociDerivativeQualifyingAsHedgeExcludedComponentParentMember_923f71ca-e448-45f3-a153-b651ad3d4a86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember_dd2dfe87-42f1-4ae4-9b9e-c0945dcf9dc9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ffa82a25-d7f4-4d53-95e1-ac183aa07165" xlink:to="loc_us-gaap_AccumulatedForeignCurrencyAdjustmentIncludingPortionAttributableToNoncontrollingInterestMember_dd2dfe87-42f1-4ae4-9b9e-c0945dcf9dc9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_6333a02f-1790-464c-bd56-3052712c523c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ffa82a25-d7f4-4d53-95e1-ac183aa07165" xlink:to="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_6333a02f-1790-464c-bd56-3052712c523c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_916f970d-a09c-4908-b762-08661ff2e8f8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ffa82a25-d7f4-4d53-95e1-ac183aa07165" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_916f970d-a09c-4908-b762-08661ff2e8f8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_b840fc53-eaec-413b-84f5-4b0d98b728c5" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_23bbf059-6042-45a9-9a67-c86dfb900c51" xlink:to="loc_dei_LegalEntityAxis_b840fc53-eaec-413b-84f5-4b0d98b728c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_b840fc53-eaec-413b-84f5-4b0d98b728c5_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_b840fc53-eaec-413b-84f5-4b0d98b728c5" xlink:to="loc_dei_EntityDomain_b840fc53-eaec-413b-84f5-4b0d98b728c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_814f82d8-0246-49c3-aaab-c95f75ff3a83" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_b840fc53-eaec-413b-84f5-4b0d98b728c5" xlink:to="loc_dei_EntityDomain_814f82d8-0246-49c3-aaab-c95f75ff3a83" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_SouthwestGasCorporationMember_5744e5b2-f167-40f3-8b48-9607a0854b81" xlink:href="swx-20220630.xsd#swx_SouthwestGasCorporationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_814f82d8-0246-49c3-aaab-c95f75ff3a83" xlink:to="loc_swx_SouthwestGasCorporationMember_5744e5b2-f167-40f3-8b48-9607a0854b81" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/SegmentInformationAccountsReceivableNotEliminatedDuringConsolidationDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#SegmentInformationAccountsReceivableNotEliminatedDuringConsolidationDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/SegmentInformationAccountsReceivableNotEliminatedDuringConsolidationDetails" xlink:type="extended" id="i224efddc7ee74b2e82a5fd15d4c9e14b_SegmentInformationAccountsReceivableNotEliminatedDuringConsolidationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_b904982d-fb67-4925-9828-20383677f565" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DueFromRelatedPartiesCurrent_527bfac1-eea9-4c3a-9f0a-acbf327ebb0e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_DueFromRelatedPartiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b904982d-fb67-4925-9828-20383677f565" xlink:to="loc_us-gaap_DueFromRelatedPartiesCurrent_527bfac1-eea9-4c3a-9f0a-acbf327ebb0e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1f37b71c-af6e-4aaa-8c79-3462ce4688ba" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_b904982d-fb67-4925-9828-20383677f565" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1f37b71c-af6e-4aaa-8c79-3462ce4688ba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_480f449a-e1b8-49d7-801e-42c7f011d749" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1f37b71c-af6e-4aaa-8c79-3462ce4688ba" xlink:to="loc_dei_LegalEntityAxis_480f449a-e1b8-49d7-801e-42c7f011d749" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_480f449a-e1b8-49d7-801e-42c7f011d749_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_480f449a-e1b8-49d7-801e-42c7f011d749" xlink:to="loc_dei_EntityDomain_480f449a-e1b8-49d7-801e-42c7f011d749_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_618a8674-4465-4a74-a83e-699255cdde16" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_480f449a-e1b8-49d7-801e-42c7f011d749" xlink:to="loc_dei_EntityDomain_618a8674-4465-4a74-a83e-699255cdde16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CenturiGroupInc.Member_39b670ff-0049-4afd-8ee9-ba51341c10e1" xlink:href="swx-20220630.xsd#swx_CenturiGroupInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_618a8674-4465-4a74-a83e-699255cdde16" xlink:to="loc_swx_CenturiGroupInc.Member_39b670ff-0049-4afd-8ee9-ba51341c10e1" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/SegmentInformationScheduleofSegmentReportingInformationDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#SegmentInformationScheduleofSegmentReportingInformationDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/SegmentInformationScheduleofSegmentReportingInformationDetails" xlink:type="extended" id="ia0b03f5f88c5471693546aca048d28ee_SegmentInformationScheduleofSegmentReportingInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_dd21db82-7e8c-499e-8cab-ca79f05f6324" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_c4e332b2-2aa0-4c68-add6-24614b4c387c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_dd21db82-7e8c-499e-8cab-ca79f05f6324" xlink:to="loc_us-gaap_Revenues_c4e332b2-2aa0-4c68-add6-24614b4c387c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_eb5da67c-0bf9-4544-8d3b-4ed2f33b90c7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_dd21db82-7e8c-499e-8cab-ca79f05f6324" xlink:to="loc_us-gaap_NetIncomeLoss_eb5da67c-0bf9-4544-8d3b-4ed2f33b90c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1ae20831-8984-47be-a77b-9d7052d62a42" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_dd21db82-7e8c-499e-8cab-ca79f05f6324" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1ae20831-8984-47be-a77b-9d7052d62a42" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_75827d96-d3cc-43b8-97bc-42f2bc984dec" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1ae20831-8984-47be-a77b-9d7052d62a42" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_75827d96-d3cc-43b8-97bc-42f2bc984dec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_75827d96-d3cc-43b8-97bc-42f2bc984dec_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_75827d96-d3cc-43b8-97bc-42f2bc984dec" xlink:to="loc_us-gaap_SegmentDomain_75827d96-d3cc-43b8-97bc-42f2bc984dec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_e3f25cdb-0640-4c62-b871-ce91a5edc462" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_75827d96-d3cc-43b8-97bc-42f2bc984dec" xlink:to="loc_us-gaap_SegmentDomain_e3f25cdb-0640-4c62-b871-ce91a5edc462" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_NaturalGasDistributionSegmentMember_f8b08e64-5b6e-4a04-a56d-3448d9feaea4" xlink:href="swx-20220630.xsd#swx_NaturalGasDistributionSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e3f25cdb-0640-4c62-b871-ce91a5edc462" xlink:to="loc_swx_NaturalGasDistributionSegmentMember_f8b08e64-5b6e-4a04-a56d-3448d9feaea4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_UtilityInfrastructureServicesSegmentMember_908110f5-3325-4364-8ffe-5b2bd91f2e98" xlink:href="swx-20220630.xsd#swx_UtilityInfrastructureServicesSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e3f25cdb-0640-4c62-b871-ce91a5edc462" xlink:to="loc_swx_UtilityInfrastructureServicesSegmentMember_908110f5-3325-4364-8ffe-5b2bd91f2e98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_PipelineAndStorageSegmentMember_6be9c78f-1304-41bb-a523-c110bfbdbf50" xlink:href="swx-20220630.xsd#swx_PipelineAndStorageSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e3f25cdb-0640-4c62-b871-ce91a5edc462" xlink:to="loc_swx_PipelineAndStorageSegmentMember_6be9c78f-1304-41bb-a523-c110bfbdbf50" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_2d878842-12f2-41e4-8ccc-713cb62b5fac" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_1ae20831-8984-47be-a77b-9d7052d62a42" xlink:to="loc_srt_ConsolidationItemsAxis_2d878842-12f2-41e4-8ccc-713cb62b5fac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_2d878842-12f2-41e4-8ccc-713cb62b5fac_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_2d878842-12f2-41e4-8ccc-713cb62b5fac" xlink:to="loc_srt_ConsolidationItemsDomain_2d878842-12f2-41e4-8ccc-713cb62b5fac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_3a8d8315-00ea-4789-aa7d-fdf8dd0838f5" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_2d878842-12f2-41e4-8ccc-713cb62b5fac" xlink:to="loc_srt_ConsolidationItemsDomain_3a8d8315-00ea-4789-aa7d-fdf8dd0838f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_51e7e666-016e-4f2c-816a-de581e7d3747" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_3a8d8315-00ea-4789-aa7d-fdf8dd0838f5" xlink:to="loc_us-gaap_OperatingSegmentsMember_51e7e666-016e-4f2c-816a-de581e7d3747" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_72f44b76-e103-4e1e-92ab-1e68b2bb7488" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MaterialReconcilingItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_3a8d8315-00ea-4789-aa7d-fdf8dd0838f5" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_72f44b76-e103-4e1e-92ab-1e68b2bb7488" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/BusinessAcquisitionsNarrativeDetail" xlink:type="simple" xlink:href="swx-20220630.xsd#BusinessAcquisitionsNarrativeDetail"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/BusinessAcquisitionsNarrativeDetail" xlink:type="extended" id="i48538d269a2b4a43aaf6ab206ae2c346_BusinessAcquisitionsNarrativeDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_ced63be7-0a5a-46f7-a7b0-40570c04e29d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_5bd8c3fd-4c99-4d62-8133-e0658399c088" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ced63be7-0a5a-46f7-a7b0-40570c04e29d" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners_5bd8c3fd-4c99-4d62-8133-e0658399c088" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts_ee46a857-f4a9-487e-8ceb-698452dee9b7" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ced63be7-0a5a-46f7-a7b0-40570c04e29d" xlink:to="loc_us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts_ee46a857-f4a9-487e-8ceb-698452dee9b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_6d682542-76c4-4ce0-9d21-eef726106840" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationAcquisitionRelatedCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ced63be7-0a5a-46f7-a7b0-40570c04e29d" xlink:to="loc_us-gaap_BusinessCombinationAcquisitionRelatedCosts_6d682542-76c4-4ce0-9d21-eef726106840" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a56c8816-0215-4afb-a8d6-92a499344426" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ced63be7-0a5a-46f7-a7b0-40570c04e29d" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a56c8816-0215-4afb-a8d6-92a499344426" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_03c9b74f-0ecd-4edc-8ee6-dfd39a764e78" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a56c8816-0215-4afb-a8d6-92a499344426" xlink:to="loc_dei_LegalEntityAxis_03c9b74f-0ecd-4edc-8ee6-dfd39a764e78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_03c9b74f-0ecd-4edc-8ee6-dfd39a764e78_default" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_03c9b74f-0ecd-4edc-8ee6-dfd39a764e78" xlink:to="loc_dei_EntityDomain_03c9b74f-0ecd-4edc-8ee6-dfd39a764e78_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_c7e45ebd-5735-4ba9-a992-6c87ffc7eab4" xlink:href="https://xbrl.sec.gov/dei/2022/dei-2022.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_03c9b74f-0ecd-4edc-8ee6-dfd39a764e78" xlink:to="loc_dei_EntityDomain_c7e45ebd-5735-4ba9-a992-6c87ffc7eab4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_CertainMembersOfRiggsDistlerManagementMember_7aa0a988-eef5-4f1a-b4e6-2efa0a3697c6" xlink:href="swx-20220630.xsd#swx_CertainMembersOfRiggsDistlerManagementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_c7e45ebd-5735-4ba9-a992-6c87ffc7eab4" xlink:to="loc_swx_CertainMembersOfRiggsDistlerManagementMember_7aa0a988-eef5-4f1a-b4e6-2efa0a3697c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_1e3ba1c4-8c40-4240-9e7d-076d6cda3573" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a56c8816-0215-4afb-a8d6-92a499344426" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_1e3ba1c4-8c40-4240-9e7d-076d6cda3573" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1e3ba1c4-8c40-4240-9e7d-076d6cda3573_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_1e3ba1c4-8c40-4240-9e7d-076d6cda3573" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1e3ba1c4-8c40-4240-9e7d-076d6cda3573_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_be41adf1-9a9d-4764-89ba-106f9ee44645" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_1e3ba1c4-8c40-4240-9e7d-076d6cda3573" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_be41adf1-9a9d-4764-89ba-106f9ee44645" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DrumMember_fe153873-605f-4afb-9631-23e909a9fb2e" xlink:href="swx-20220630.xsd#swx_DrumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_be41adf1-9a9d-4764-89ba-106f9ee44645" xlink:to="loc_swx_DrumMember_fe153873-605f-4afb-9631-23e909a9fb2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DominionEnergyQuestarPipelineLLCMember_ca7539c6-1790-4d19-b060-8febbe34a0d7" xlink:href="swx-20220630.xsd#swx_DominionEnergyQuestarPipelineLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_be41adf1-9a9d-4764-89ba-106f9ee44645" xlink:to="loc_swx_DominionEnergyQuestarPipelineLLCMember_ca7539c6-1790-4d19-b060-8febbe34a0d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipAxis_0b5907a1-a74a-4f86-ac9f-24bb74fdc800" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a56c8816-0215-4afb-a8d6-92a499344426" xlink:to="loc_srt_OwnershipAxis_0b5907a1-a74a-4f86-ac9f-24bb74fdc800" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_0b5907a1-a74a-4f86-ac9f-24bb74fdc800_default" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_OwnershipAxis_0b5907a1-a74a-4f86-ac9f-24bb74fdc800" xlink:to="loc_srt_OwnershipDomain_0b5907a1-a74a-4f86-ac9f-24bb74fdc800_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_OwnershipDomain_2f9e7310-97ed-4b77-a6c2-8da433b3aab7" xlink:href="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd#srt_OwnershipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_OwnershipAxis_0b5907a1-a74a-4f86-ac9f-24bb74fdc800" xlink:to="loc_srt_OwnershipDomain_2f9e7310-97ed-4b77-a6c2-8da433b3aab7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DrumMember_efec997b-607c-444f-b177-13e6615fde7b" xlink:href="swx-20220630.xsd#swx_DrumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_OwnershipDomain_2f9e7310-97ed-4b77-a6c2-8da433b3aab7" xlink:to="loc_swx_DrumMember_efec997b-607c-444f-b177-13e6615fde7b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/BusinessAcquisitionsSummaryofAssetsAcquiredandLiabilitiesAssumedDrumAcquisitionDetail" xlink:type="simple" xlink:href="swx-20220630.xsd#BusinessAcquisitionsSummaryofAssetsAcquiredandLiabilitiesAssumedDrumAcquisitionDetail"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/BusinessAcquisitionsSummaryofAssetsAcquiredandLiabilitiesAssumedDrumAcquisitionDetail" xlink:type="extended" id="i3157391350af45aba70c296ae59d32db_BusinessAcquisitionsSummaryofAssetsAcquiredandLiabilitiesAssumedDrumAcquisitionDetail">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_9b67618e-c823-4ca8-925d-0061859f3926" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9b67618e-c823-4ca8-925d-0061859f3926" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_8a26132c-ff01-4170-9971-266c08e8bd7d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_8a26132c-ff01-4170-9971-266c08e8bd7d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_7563f97f-4678-416a-8f3a-205a16781404" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_7563f97f-4678-416a-8f3a-205a16781404" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets_750c6337-c8da-4fe2-8eee-9649e878e6c6" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractAssets_750c6337-c8da-4fe2-8eee-9649e878e6c6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIncomeTaxesReceivableNet_1c510c2a-8456-41b7-bf3f-f34aaed19230" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIncomeTaxesReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIncomeTaxesReceivableNet_1c510c2a-8456-41b7-bf3f-f34aaed19230" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseAssetsUnderOperatingLeases_4151eb07-9dbe-410e-acf5-a5e95dd50e2f" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseAssetsUnderOperatingLeases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRightOfUseAssetsUnderOperatingLeases_4151eb07-9dbe-410e-acf5-a5e95dd50e2f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_4e547566-3c8c-49a1-b88c-13a6138e7343" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_4e547566-3c8c-49a1-b88c-13a6138e7343" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_d37a9fa9-203e-4a1e-8caa-d7399307813c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_d37a9fa9-203e-4a1e-8caa-d7399307813c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_34ad99d6-6bf5-4bb0-9bae-dc51f0aac03a" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_34ad99d6-6bf5-4bb0-9bae-dc51f0aac03a" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_2a94d7fe-f728-493c-a03e-2878ce19ef63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_Goodwill_2a94d7fe-f728-493c-a03e-2878ce19ef63" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAndGoodwill_fbcaa87b-4224-4f0d-a46a-1f7b2ebe5b97" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAndGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAndGoodwill_fbcaa87b-4224-4f0d-a46a-1f7b2ebe5b97" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_f218f362-9239-4896-b5e7-406728a635bc" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_f218f362-9239-4896-b5e7-406728a635bc" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseObligations_00fafc46-1a37-470c-8a04-3716b8ff6140" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedFinanceLeaseObligations_00fafc46-1a37-470c-8a04-3716b8ff6140" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractLiabilities_313c48fb-ef77-406b-a49e-4cbfc103b7eb" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedContractLiabilities_313c48fb-ef77-406b-a49e-4cbfc103b7eb" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseObligations_598db2ab-063f-454c-a83c-1596115446a8" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOperatingLeaseObligations_598db2ab-063f-454c-a83c-1596115446a8" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_a93d43f2-9d98-4093-a46a-6eed38bae9e3" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_a93d43f2-9d98-4093-a46a-6eed38bae9e3" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_4e9103e5-a195-4bfa-87ad-1d4d064bd44c" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_4e9103e5-a195-4bfa-87ad-1d4d064bd44c" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_d184b4ca-b710-46de-bd0c-162839d6f2ef" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_d184b4ca-b710-46de-bd0c-162839d6f2ef" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_35935118-ba1f-4b3a-99ea-d0ba65b92711" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_35935118-ba1f-4b3a-99ea-d0ba65b92711" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivableNet_753e0179-cd24-48fb-8a75-0d49f85eb164" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivableNet_753e0179-cd24-48fb-8a75-0d49f85eb164" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentContractAssets_1c3520d0-d5e8-468c-8d54-38836fe9de59" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentContractAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentContractAssets_1c3520d0-d5e8-468c-8d54-38836fe9de59" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment_f6af4d2a-443f-4814-bea3-677dbbc2b113" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentPropertyPlantAndEquipment_f6af4d2a-443f-4814-bea3-677dbbc2b113" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles_1e278ab4-4d88-4e7b-853c-2df05e6eacae" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentIntangibles_1e278ab4-4d88-4e7b-853c-2df05e6eacae" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_ff2f5ed7-5879-4d7d-8588-0a7288515766" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_ff2f5ed7-5879-4d7d-8588-0a7288515766" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAssets_dc8b65b2-8f2d-4130-8401-d9b15344b542" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAssets_dc8b65b2-8f2d-4130-8401-d9b15344b542" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinanceLeaseObligations_0981c13a-164c-4f72-ac10-2025084cec01" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinanceLeaseObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentFinanceLeaseObligations_0981c13a-164c-4f72-ac10-2025084cec01" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncurrentLiabilitiesOther_6c9b0b67-6215-4f9a-acc8-c59b2ad9ae25" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentNoncurrentLiabilitiesOther_6c9b0b67-6215-4f9a-acc8-c59b2ad9ae25" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredTaxLiabilities_1022bdd2-cc8c-4a42-8ecc-b44f421939a2" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredTaxLiabilities_1022bdd2-cc8c-4a42-8ecc-b44f421939a2" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentLiabilities_3f7fb44c-6937-419d-b66a-8e98ff07ea65" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentLiabilities_3f7fb44c-6937-419d-b66a-8e98ff07ea65" xlink:type="arc" order="28"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred_b1388c00-cb07-42f6-bd99-d085cff91515" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNetAbstract_fd9c0a98-5dde-4e64-895c-ee5bcd1a5da3" xlink:to="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred_b1388c00-cb07-42f6-bd99-d085cff91515" xlink:type="arc" order="29"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57babcda-ffa0-4f75-9e83-63b07c25184f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_9b67618e-c823-4ca8-925d-0061859f3926" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57babcda-ffa0-4f75-9e83-63b07c25184f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_86bec6d8-f536-4ed0-854e-0077b298ebbb" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_57babcda-ffa0-4f75-9e83-63b07c25184f" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_86bec6d8-f536-4ed0-854e-0077b298ebbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_86bec6d8-f536-4ed0-854e-0077b298ebbb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_86bec6d8-f536-4ed0-854e-0077b298ebbb" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_86bec6d8-f536-4ed0-854e-0077b298ebbb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a6335d0d-8b5d-42f9-9647-79fecccdef96" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_86bec6d8-f536-4ed0-854e-0077b298ebbb" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a6335d0d-8b5d-42f9-9647-79fecccdef96" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DrumMember_5c68303c-dc63-4081-8dc3-3dfe3764eb25" xlink:href="swx-20220630.xsd#swx_DrumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a6335d0d-8b5d-42f9-9647-79fecccdef96" xlink:to="loc_swx_DrumMember_5c68303c-dc63-4081-8dc3-3dfe3764eb25" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.swgas.com/role/BusinessAcquisitionsSummaryofAssetsAcquiredandLiabilitiesAssumedQuestarAcquisitionDetails" xlink:type="simple" xlink:href="swx-20220630.xsd#BusinessAcquisitionsSummaryofAssetsAcquiredandLiabilitiesAssumedQuestarAcquisitionDetails"/>
  <link:definitionLink xlink:role="http://www.swgas.com/role/BusinessAcquisitionsSummaryofAssetsAcquiredandLiabilitiesAssumedQuestarAcquisitionDetails" xlink:type="extended" id="i3a1c4a8312524f4e8be9c535bfea1856_BusinessAcquisitionsSummaryofAssetsAcquiredandLiabilitiesAssumedQuestarAcquisitionDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedGasPlantNet_baf31db8-2a09-4c88-97f5-f9ae0aad5bf6" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedGasPlantNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedGasPlantNet_baf31db8-2a09-4c88-97f5-f9ae0aad5bf6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherPropertyAndInvestments_1a240dc6-a068-4af9-90a1-5f0f57c2c2e3" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherPropertyAndInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherPropertyAndInvestments_1a240dc6-a068-4af9-90a1-5f0f57c2c2e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_ba01b2aa-72f9-4c83-b9aa-14d41eef0975" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_ba01b2aa-72f9-4c83-b9aa-14d41eef0975" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_b2a39023-3013-4cbb-94ba-e44299dbb247" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_b2a39023-3013-4cbb-94ba-e44299dbb247" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_e8c0b97c-3e6c-41aa-a9b0-635c29a33c3b" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_e8c0b97c-3e6c-41aa-a9b0-635c29a33c3b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredChargesAndOtherAssets_e41292c0-43e2-4adf-848c-2cb893ac8087" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredChargesAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredChargesAndOtherAssets_e41292c0-43e2-4adf-848c-2cb893ac8087" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_88918146-4c5e-41a7-a806-4c71d01fe5a8" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_Goodwill_88918146-4c5e-41a7-a806-4c71d01fe5a8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_5892742b-4378-4727-a76e-7ef65d0b8d91" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_5892742b-4378-4727-a76e-7ef65d0b8d91" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_782f3413-b746-4549-80fd-aa2e2540dcd6" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAcquiredIncludingGoodwill_782f3413-b746-4549-80fd-aa2e2540dcd6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_e7e96298-dbeb-4c87-90f5-78b6a0768dd5" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesLongTermDebt_e7e96298-dbeb-4c87-90f5-78b6a0768dd5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_a48af8e6-9d6f-4721-863f-2fda24bca48d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_a48af8e6-9d6f-4721-863f-2fda24bca48d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredPurchasedGasCosts_4c81417a-d297-47b5-87e8-34c347ce592e" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredPurchasedGasCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredPurchasedGasCosts_4c81417a-d297-47b5-87e8-34c347ce592e" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCustomerDeposits_7def26eb-7eae-4bf9-86a3-b1989f37f036" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCustomerDeposits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCustomerDeposits_7def26eb-7eae-4bf9-86a3-b1989f37f036" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedGeneralTaxes_635c1d74-e5f1-4f31-baf4-192b2fb1ada9" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedGeneralTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedGeneralTaxes_635c1d74-e5f1-4f31-baf4-192b2fb1ada9" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedInterest_31ccdef2-42dd-40b4-b30a-7f87aa6859b7" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedInterest_31ccdef2-42dd-40b4-b30a-7f87aa6859b7" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_71890734-11c2-4d9b-9077-76132835371d" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_71890734-11c2-4d9b-9077-76132835371d" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccumulatedRemovalCosts_141cabc1-4210-40b3-9855-2daa98cf8efc" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccumulatedRemovalCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccumulatedRemovalCosts_141cabc1-4210-40b3-9855-2daa98cf8efc" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherDeferredCredits_a80fdb66-54d3-4a24-aece-6597539fbf29" xlink:href="swx-20220630.xsd#swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherDeferredCredits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherDeferredCredits_a80fdb66-54d3-4a24-aece-6597539fbf29" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_27d5b78c-e181-47cf-881c-5b151050b34f" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_27d5b78c-e181-47cf-881c-5b151050b34f" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_b1d413de-0dd6-4d2d-b858-80718384bb32" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_b1d413de-0dd6-4d2d-b858-80718384bb32" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivableNet_0ac40dc4-8dc7-4fe5-a2b0-ff172543405d" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAccountsReceivableNet_0ac40dc4-8dc7-4fe5-a2b0-ff172543405d" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_3bf98e48-95d4-4bea-b25d-fe480e509b4e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_3bf98e48-95d4-4bea-b25d-fe480e509b4e" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredIncomeTaxes_3a3573c1-41a0-46c9-bad4-53106543a298" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredIncomeTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentDeferredIncomeTaxes_3a3573c1-41a0-46c9-bad4-53106543a298" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAssets_e0ecad01-e214-477d-977e-114b3fd4cc9e" xlink:href="swx-20220630.xsd#swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_swx_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAssets_e0ecad01-e214-477d-977e-114b3fd4cc9e" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred_8873a2e3-02ec-4f58-bbf0-43d7b4eae3c9" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred_8873a2e3-02ec-4f58-bbf0-43d7b4eae3c9" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_87309df8-76e1-4b8e-b2b2-b0bb3e5a3c7e" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_ded5e48c-cf60-4014-8643-321420c91562" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_87309df8-76e1-4b8e-b2b2-b0bb3e5a3c7e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_1bdcf24b-a437-472a-94be-31eda9f25b63" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_87309df8-76e1-4b8e-b2b2-b0bb3e5a3c7e" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_1bdcf24b-a437-472a-94be-31eda9f25b63" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1bdcf24b-a437-472a-94be-31eda9f25b63_default" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_1bdcf24b-a437-472a-94be-31eda9f25b63" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1bdcf24b-a437-472a-94be-31eda9f25b63_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_04339a0f-bee9-45fa-9ae1-a763af645b16" xlink:href="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_1bdcf24b-a437-472a-94be-31eda9f25b63" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_04339a0f-bee9-45fa-9ae1-a763af645b16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_swx_DominionEnergyQuestarPipelineLLCMember_b9f56222-53bc-4d37-a7ba-4f3c35256f09" xlink:href="swx-20220630.xsd#swx_DominionEnergyQuestarPipelineLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_04339a0f-bee9-45fa-9ae1-a763af645b16" xlink:to="loc_swx_DominionEnergyQuestarPipelineLLCMember_b9f56222-53bc-4d37-a7ba-4f3c35256f09" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
