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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:87a8844e-d779-4108-906f-b29d9bc7324f,g:16e1831a-ad87-49cf-8134-449c5e2b0c8e-->
<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.commvault.com/role/ConsolidatedStatementsofOperations" xlink:type="simple" xlink:href="cvlt-20250630.xsd#ConsolidatedStatementsofOperations"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/ConsolidatedStatementsofOperations" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_6e8a2cb4-5e9c-47c9-bbc5-a81116942a6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_StatementTable_6e8a2cb4-5e9c-47c9-bbc5-a81116942a6c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_4b562d71-160e-4f87-a505-dc095981dcff" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_6e8a2cb4-5e9c-47c9-bbc5-a81116942a6c" xlink:to="loc_srt_ProductOrServiceAxis_4b562d71-160e-4f87-a505-dc095981dcff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_4b562d71-160e-4f87-a505-dc095981dcff_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_4b562d71-160e-4f87-a505-dc095981dcff" xlink:to="loc_srt_ProductsAndServicesDomain_4b562d71-160e-4f87-a505-dc095981dcff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_d6960ebe-e050-4b88-b536-e4e3be8510bd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_4b562d71-160e-4f87-a505-dc095981dcff" xlink:to="loc_srt_ProductsAndServicesDomain_d6960ebe-e050-4b88-b536-e4e3be8510bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SubscriptionMember_dcbb65ee-94d6-48dc-85ed-3872bc782ca2" xlink:href="cvlt-20250630.xsd#cvlt_SubscriptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d6960ebe-e050-4b88-b536-e4e3be8510bd" xlink:to="loc_cvlt_SubscriptionMember_dcbb65ee-94d6-48dc-85ed-3872bc782ca2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_TermBasedSoftwareLicensesMember_525a21e5-3984-407b-a699-ff7d88c3f1a3" xlink:href="cvlt-20250630.xsd#cvlt_TermBasedSoftwareLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_SubscriptionMember_dcbb65ee-94d6-48dc-85ed-3872bc782ca2" xlink:to="loc_cvlt_TermBasedSoftwareLicensesMember_525a21e5-3984-407b-a699-ff7d88c3f1a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SoftwareAsAServiceMember_23fcd618-414e-44e7-9ffb-154ded71e686" xlink:href="cvlt-20250630.xsd#cvlt_SoftwareAsAServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_SubscriptionMember_dcbb65ee-94d6-48dc-85ed-3872bc782ca2" xlink:to="loc_cvlt_SoftwareAsAServiceMember_23fcd618-414e-44e7-9ffb-154ded71e686" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_PerpetualLicenseMember_42cfffb9-1524-4753-abb3-9743869d45f9" xlink:href="cvlt-20250630.xsd#cvlt_PerpetualLicenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d6960ebe-e050-4b88-b536-e4e3be8510bd" xlink:to="loc_cvlt_PerpetualLicenseMember_42cfffb9-1524-4753-abb3-9743869d45f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CustomerSupportServiceMember_e5e02838-da5d-4790-b3a9-a8c764b645cf" xlink:href="cvlt-20250630.xsd#cvlt_CustomerSupportServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d6960ebe-e050-4b88-b536-e4e3be8510bd" xlink:to="loc_cvlt_CustomerSupportServiceMember_e5e02838-da5d-4790-b3a9-a8c764b645cf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceOtherMember_765af102-001b-4ff2-95b4-44a503fb0124" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_d6960ebe-e050-4b88-b536-e4e3be8510bd" xlink:to="loc_us-gaap_ServiceOtherMember_765af102-001b-4ff2-95b4-44a503fb0124" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerAbstract_591aef39-bd79-40c6-a890-980a1d646292" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerAbstract_591aef39-bd79-40c6-a890-980a1d646292" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_eeab2266-e698-41da-8d0a-2774b7a225f2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueFromContractWithCustomerAbstract_591aef39-bd79-40c6-a890-980a1d646292" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_eeab2266-e698-41da-8d0a-2774b7a225f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSoldAbstract_53ff6faa-661f-4542-aecf-401962695e42" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSoldAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSoldAbstract_53ff6faa-661f-4542-aecf-401962695e42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_8d28f7c9-db6b-4507-a4e4-93fdfc36367a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostOfGoodsAndServicesSoldAbstract_53ff6faa-661f-4542-aecf-401962695e42" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_8d28f7c9-db6b-4507-a4e4-93fdfc36367a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_58c3a94b-2dc6-43eb-b17b-c6ac5260441f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_GrossProfit_58c3a94b-2dc6-43eb-b17b-c6ac5260441f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpense_b19239cc-01ec-4e0e-8d4e-45b6b2b1ed04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingAndMarketingExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:to="loc_us-gaap_SellingAndMarketingExpense_b19239cc-01ec-4e0e-8d4e-45b6b2b1ed04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_bf4948e5-6f00-47e0-bc0f-a3d27f01b098" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_bf4948e5-6f00-47e0-bc0f-a3d27f01b098" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_227bb9e0-7228-454b-912d-ddcd6484e633" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_227bb9e0-7228-454b-912d-ddcd6484e633" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_66de5f07-da51-4375-9e5c-3c913c889230" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:to="loc_us-gaap_DepreciationAndAmortization_66de5f07-da51-4375-9e5c-3c913c889230" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_9c25ff0f-3dc4-4af9-959b-f1bcb435e3fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:to="loc_us-gaap_RestructuringCharges_9c25ff0f-3dc4-4af9-959b-f1bcb435e3fb" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_7e0dbe60-17b2-4baf-b119-41093301d25b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_7e0dbe60-17b2-4baf-b119-41093301d25b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_fd67b687-855d-44a8-a39a-2d7c14f22f5e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_b15b2c09-cbb8-47d1-b1a8-057ba010ffea" xlink:to="loc_us-gaap_OperatingExpenses_fd67b687-855d-44a8-a39a-2d7c14f22f5e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_5ed479b1-c2ca-4178-84c1-c6e0baf2cfb0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_OperatingIncomeLoss_5ed479b1-c2ca-4178-84c1-c6e0baf2cfb0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeInterest_ca1dd230-d548-4503-ae57-d4d7024807a2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InvestmentIncomeInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_InvestmentIncomeInterest_ca1dd230-d548-4503-ae57-d4d7024807a2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_a9f3a74b-ede9-4e81-b49f-ab4b3e4c47d8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_InterestExpenseNonoperating_a9f3a74b-ede9-4e81-b49f-ab4b3e4c47d8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_0dedf38d-051d-4c96-8d5d-e5f37acdb9b6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_0dedf38d-051d-4c96-8d5d-e5f37acdb9b6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_46a00e1c-15a2-41c0-b542-746bfb91acb5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_46a00e1c-15a2-41c0-b542-746bfb91acb5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_d993b707-6c99-477a-8acd-88ef2741f1ca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_d993b707-6c99-477a-8acd-88ef2741f1ca" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_232489fe-64a3-4722-9f44-b45bb775631f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_NetIncomeLoss_232489fe-64a3-4722-9f44-b45bb775631f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_d45744ca-387a-41c3-ac39-8ca131960141" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_EarningsPerShareAbstract_d45744ca-387a-41c3-ac39-8ca131960141" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_9a022adb-676b-4e26-92d0-dd18923c3d31" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_d45744ca-387a-41c3-ac39-8ca131960141" xlink:to="loc_us-gaap_EarningsPerShareBasic_9a022adb-676b-4e26-92d0-dd18923c3d31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_645b7531-7868-4b42-91f4-379c4e72922f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_d45744ca-387a-41c3-ac39-8ca131960141" xlink:to="loc_us-gaap_EarningsPerShareDiluted_645b7531-7868-4b42-91f4-379c4e72922f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_50c80b55-0092-4b14-8ff9-0011481c84f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_b9812410-f103-4164-b537-52f065acb570" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_50c80b55-0092-4b14-8ff9-0011481c84f7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_190bec4d-e540-4b27-b745-48d8b695c9e6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_50c80b55-0092-4b14-8ff9-0011481c84f7" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_190bec4d-e540-4b27-b745-48d8b695c9e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_d4a9aade-4397-4452-9aca-441219000a6e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_50c80b55-0092-4b14-8ff9-0011481c84f7" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_d4a9aade-4397-4452-9aca-441219000a6e" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="simple" xlink:href="cvlt-20250630.xsd#ConsolidatedStatementsofStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_3294fdda-1caa-4937-8ffd-24a0e1f635c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_cc442968-8ec6-4aec-8726-531125777a2a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_3294fdda-1caa-4937-8ffd-24a0e1f635c1" xlink:to="loc_us-gaap_StatementTable_cc442968-8ec6-4aec-8726-531125777a2a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_b413517f-bffa-4b98-bc2b-cbd8591c760c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_cc442968-8ec6-4aec-8726-531125777a2a" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_b413517f-bffa-4b98-bc2b-cbd8591c760c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_b413517f-bffa-4b98-bc2b-cbd8591c760c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_b413517f-bffa-4b98-bc2b-cbd8591c760c" xlink:to="loc_us-gaap_EquityComponentDomain_b413517f-bffa-4b98-bc2b-cbd8591c760c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_0d05395e-016a-4d99-b28e-24a627f15cca" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_b413517f-bffa-4b98-bc2b-cbd8591c760c" xlink:to="loc_us-gaap_EquityComponentDomain_0d05395e-016a-4d99-b28e-24a627f15cca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_4753205b-2cb7-4a46-b25c-c94e766bac1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0d05395e-016a-4d99-b28e-24a627f15cca" xlink:to="loc_us-gaap_CommonStockMember_4753205b-2cb7-4a46-b25c-c94e766bac1c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_6fe8a201-9200-4ed6-bfc3-02761ec4c396" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0d05395e-016a-4d99-b28e-24a627f15cca" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_6fe8a201-9200-4ed6-bfc3-02761ec4c396" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_b111c68e-cbcf-4108-bc12-a2dac7ce5ff7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0d05395e-016a-4d99-b28e-24a627f15cca" xlink:to="loc_us-gaap_RetainedEarningsMember_b111c68e-cbcf-4108-bc12-a2dac7ce5ff7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_7fb2cce9-e4b4-4f6f-a369-28857b6da852" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_0d05395e-016a-4d99-b28e-24a627f15cca" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_7fb2cce9-e4b4-4f6f-a369-28857b6da852" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_3294fdda-1caa-4937-8ffd-24a0e1f635c1" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_90fe8880-a7af-46d1-bfdc-78f13d3ef770" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_90fe8880-a7af-46d1-bfdc-78f13d3ef770" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_93efa770-71c7-4e93-8e9c-657798cd3b27" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_StockholdersEquity_93efa770-71c7-4e93-8e9c-657798cd3b27" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_d97e4a11-0441-42a7-94e0-c53a1b43b10a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_d97e4a11-0441-42a7-94e0-c53a1b43b10a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_63c42c11-d4a5-439a-9587-fdc26dc3bbaa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_63c42c11-d4a5-439a-9587-fdc26dc3bbaa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_ffa574ab-1817-4ef3-8c45-59ead0e8a141" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_ffa574ab-1817-4ef3-8c45-59ead0e8a141" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_0e82a2e4-6da6-4f5b-b623-0abbc384136d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_0e82a2e4-6da6-4f5b-b623-0abbc384136d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_66bf4a55-9df8-42e1-ac04-4aabe50f1fa4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensation_66bf4a55-9df8-42e1-ac04-4aabe50f1fa4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_26b50a2a-f57d-4c45-b27a-050b181a2f4b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodShares_26b50a2a-f57d-4c45-b27a-050b181a2f4b" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_dc65dd53-30ef-4d27-a158-2c86ea938827" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_StockRepurchasedAndRetiredDuringPeriodValue_dc65dd53-30ef-4d27-a158-2c86ea938827" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_e09e7172-f27d-4b0e-a974-5424a5b77566" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_NetIncomeLoss_e09e7172-f27d-4b0e-a974-5424a5b77566" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_16c7a5cc-85b0-422d-afc6-a6b060939a0c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_453cc7e3-1b09-4556-b878-e5c6c6c0a012" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_16c7a5cc-85b0-422d-afc6-a6b060939a0c" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_98a3bb10-93ea-4674-89d6-f826432882e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_7fb6e188-44e5-4d84-bf9f-673c6324729c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/SummaryofSignificantAccountingPoliciesConcentrationofCreditRiskDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#SummaryofSignificantAccountingPoliciesConcentrationofCreditRiskDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/SummaryofSignificantAccountingPoliciesConcentrationofCreditRiskDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_5011e82b-a109-4d10-a436-5886bf69711a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_a08be1f2-0b3c-499d-94b7-47a6ef802b91" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_5011e82b-a109-4d10-a436-5886bf69711a" xlink:to="loc_us-gaap_ConcentrationRiskTable_a08be1f2-0b3c-499d-94b7-47a6ef802b91" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_327754b7-838f-4b54-85bf-4c8b0d99c711" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_a08be1f2-0b3c-499d-94b7-47a6ef802b91" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_327754b7-838f-4b54-85bf-4c8b0d99c711" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_327754b7-838f-4b54-85bf-4c8b0d99c711_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_327754b7-838f-4b54-85bf-4c8b0d99c711" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_327754b7-838f-4b54-85bf-4c8b0d99c711_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_bbfa48f1-1c27-45fc-a481-b2905767bccc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_327754b7-838f-4b54-85bf-4c8b0d99c711" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_bbfa48f1-1c27-45fc-a481-b2905767bccc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_462de16a-920d-4464-88d8-014409c42fe4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_bbfa48f1-1c27-45fc-a481-b2905767bccc" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_462de16a-920d-4464-88d8-014409c42fe4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MajorCustomersAxis_1b913803-620e-4eff-b9d3-ed30834950ec" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MajorCustomersAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_a08be1f2-0b3c-499d-94b7-47a6ef802b91" xlink:to="loc_srt_MajorCustomersAxis_1b913803-620e-4eff-b9d3-ed30834950ec" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_1b913803-620e-4eff-b9d3-ed30834950ec_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_MajorCustomersAxis_1b913803-620e-4eff-b9d3-ed30834950ec" xlink:to="loc_srt_NameOfMajorCustomerDomain_1b913803-620e-4eff-b9d3-ed30834950ec_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_NameOfMajorCustomerDomain_7550ffbf-a054-41bd-9eec-2807a9a95088" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_NameOfMajorCustomerDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_MajorCustomersAxis_1b913803-620e-4eff-b9d3-ed30834950ec" xlink:to="loc_srt_NameOfMajorCustomerDomain_7550ffbf-a054-41bd-9eec-2807a9a95088" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CustomerAMember_72c39cc2-b1e7-4a4d-9b1b-1d4407c3f944" xlink:href="cvlt-20250630.xsd#cvlt_CustomerAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_7550ffbf-a054-41bd-9eec-2807a9a95088" xlink:to="loc_cvlt_CustomerAMember_72c39cc2-b1e7-4a4d-9b1b-1d4407c3f944" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CustomerBMember_0e97f817-183f-46ce-b7f2-16c1851e2179" xlink:href="cvlt-20250630.xsd#cvlt_CustomerBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_NameOfMajorCustomerDomain_7550ffbf-a054-41bd-9eec-2807a9a95088" xlink:to="loc_cvlt_CustomerBMember_0e97f817-183f-46ce-b7f2-16c1851e2179" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_b63f7c77-cd3f-4203-b28c-bee61c29e12f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_a08be1f2-0b3c-499d-94b7-47a6ef802b91" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_b63f7c77-cd3f-4203-b28c-bee61c29e12f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b63f7c77-cd3f-4203-b28c-bee61c29e12f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_b63f7c77-cd3f-4203-b28c-bee61c29e12f" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_b63f7c77-cd3f-4203-b28c-bee61c29e12f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1c1de56d-99af-4409-bcd4-16f7692ebf74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_b63f7c77-cd3f-4203-b28c-bee61c29e12f" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1c1de56d-99af-4409-bcd4-16f7692ebf74" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SalesRevenueNetMember_f7bc9948-f3e1-4db2-809b-1c325e8fa7f0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SalesRevenueNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1c1de56d-99af-4409-bcd4-16f7692ebf74" xlink:to="loc_us-gaap_SalesRevenueNetMember_f7bc9948-f3e1-4db2-809b-1c325e8fa7f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableMember_7453475c-44be-4aa5-b6bd-7dd52d9d4a05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_1c1de56d-99af-4409-bcd4-16f7692ebf74" xlink:to="loc_us-gaap_AccountsReceivableMember_7453475c-44be-4aa5-b6bd-7dd52d9d4a05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_c9165215-f17a-4e55-a331-e37d1572a214" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_5011e82b-a109-4d10-a436-5886bf69711a" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_c9165215-f17a-4e55-a331-e37d1572a214" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/SummaryofSignificantAccountingPoliciesSummaryofFairValueofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#SummaryofSignificantAccountingPoliciesSummaryofFairValueofFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/SummaryofSignificantAccountingPoliciesSummaryofFairValueofFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_cb88254d-1501-4510-9a07-c607db338513" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e7472bd9-ca76-482f-ad6f-603e374856c7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_cb88254d-1501-4510-9a07-c607db338513" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e7472bd9-ca76-482f-ad6f-603e374856c7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_4cb48c9c-3346-4cd7-87c6-45e4b29eb63c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e7472bd9-ca76-482f-ad6f-603e374856c7" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_4cb48c9c-3346-4cd7-87c6-45e4b29eb63c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4cb48c9c-3346-4cd7-87c6-45e4b29eb63c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_4cb48c9c-3346-4cd7-87c6-45e4b29eb63c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_4cb48c9c-3346-4cd7-87c6-45e4b29eb63c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3dd75567-7f72-4dd3-a640-52b79f7337d5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_4cb48c9c-3346-4cd7-87c6-45e4b29eb63c" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3dd75567-7f72-4dd3-a640-52b79f7337d5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_a0108f91-c1d6-48ee-8d9d-7f4e5c9a5ff3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3dd75567-7f72-4dd3-a640-52b79f7337d5" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_a0108f91-c1d6-48ee-8d9d-7f4e5c9a5ff3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_9dbcc914-cee7-4098-b143-3ea7cc0c6521" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3dd75567-7f72-4dd3-a640-52b79f7337d5" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_9dbcc914-cee7-4098-b143-3ea7cc0c6521" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_2355eb1b-af95-4457-a11d-7e0e03959108" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3dd75567-7f72-4dd3-a640-52b79f7337d5" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_2355eb1b-af95-4457-a11d-7e0e03959108" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosureAbstract_29d323ca-2843-46b6-9ca1-2343c066698d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AssetsFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_cb88254d-1501-4510-9a07-c607db338513" xlink:to="loc_us-gaap_AssetsFairValueDisclosureAbstract_29d323ca-2843-46b6-9ca1-2343c066698d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_3e59276f-89bf-4010-bede-48a4eb8d11be" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsFairValueDisclosureAbstract_29d323ca-2843-46b6-9ca1-2343c066698d" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount_3e59276f-89bf-4010-bede-48a4eb8d11be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_74e1b4f8-3fb5-4098-bf82-ff5c0a7493d6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LiabilitiesFairValueDisclosureAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_cb88254d-1501-4510-9a07-c607db338513" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_74e1b4f8-3fb5-4098-bf82-ff5c0a7493d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_dec34e40-222b-44c9-910e-bc931adcc2a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesFairValueDisclosureAbstract_74e1b4f8-3fb5-4098-bf82-ff5c0a7493d6" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_dec34e40-222b-44c9-910e-bc931adcc2a0" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/SummaryofSignificantAccountingPoliciesFairValueofFinancialInstrumentsDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#SummaryofSignificantAccountingPoliciesFairValueofFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/SummaryofSignificantAccountingPoliciesFairValueofFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_87a82ce5-8d16-4187-94c2-3fcb3386d06e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e1a895d4-b38a-4ec4-a6d2-29be6f1a2b74" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_87a82ce5-8d16-4187-94c2-3fcb3386d06e" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e1a895d4-b38a-4ec4-a6d2-29be6f1a2b74" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_0c3bd34a-3734-4cf8-b3bb-8d886e7cb7ad" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e1a895d4-b38a-4ec4-a6d2-29be6f1a2b74" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_0c3bd34a-3734-4cf8-b3bb-8d886e7cb7ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0c3bd34a-3734-4cf8-b3bb-8d886e7cb7ad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_0c3bd34a-3734-4cf8-b3bb-8d886e7cb7ad" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_0c3bd34a-3734-4cf8-b3bb-8d886e7cb7ad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_04190277-8a8b-4747-802c-e6f4e70bd53a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_0c3bd34a-3734-4cf8-b3bb-8d886e7cb7ad" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_04190277-8a8b-4747-802c-e6f4e70bd53a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_f2774451-11bf-4c56-a19b-c88863d9b274" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_04190277-8a8b-4747-802c-e6f4e70bd53a" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_f2774451-11bf-4c56-a19b-c88863d9b274" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_648fa872-92e6-4772-af82-2fc3fd5412a0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e1a895d4-b38a-4ec4-a6d2-29be6f1a2b74" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_648fa872-92e6-4772-af82-2fc3fd5412a0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_648fa872-92e6-4772-af82-2fc3fd5412a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_648fa872-92e6-4772-af82-2fc3fd5412a0" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_648fa872-92e6-4772-af82-2fc3fd5412a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8c82e5ab-e62d-4354-9e8a-8b6c41456e07" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_648fa872-92e6-4772-af82-2fc3fd5412a0" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8c82e5ab-e62d-4354-9e8a-8b6c41456e07" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_AppranixIncMember_3f9e5929-a24b-4a12-8a8c-5ce47351834f" xlink:href="cvlt-20250630.xsd#cvlt_AppranixIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8c82e5ab-e62d-4354-9e8a-8b6c41456e07" xlink:to="loc_cvlt_AppranixIncMember_3f9e5929-a24b-4a12-8a8c-5ce47351834f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_BusinessCombinationConsiderationTransferredContingentConsideration_9cbf5015-63b4-4555-a732-71a853d398c0" xlink:href="cvlt-20250630.xsd#cvlt_BusinessCombinationConsiderationTransferredContingentConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_87a82ce5-8d16-4187-94c2-3fcb3386d06e" xlink:to="loc_cvlt_BusinessCombinationConsiderationTransferredContingentConsideration_9cbf5015-63b4-4555-a732-71a853d398c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_PaymentForContingentConsiderationLiability_7903c099-0cc3-4ab1-882f-60d8aeef1c66" xlink:href="cvlt-20250630.xsd#cvlt_PaymentForContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_87a82ce5-8d16-4187-94c2-3fcb3386d06e" xlink:to="loc_cvlt_PaymentForContingentConsiderationLiability_7903c099-0cc3-4ab1-882f-60d8aeef1c66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_9bde9587-4f1a-4a88-b2c9-c1c480776916" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_87a82ce5-8d16-4187-94c2-3fcb3386d06e" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_9bde9587-4f1a-4a88-b2c9-c1c480776916" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_3948e806-f06b-4a43-bafd-a9bd7f20cbc1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_87a82ce5-8d16-4187-94c2-3fcb3386d06e" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_3948e806-f06b-4a43-bafd-a9bd7f20cbc1" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/SummaryofSignificantAccountingPoliciesGoodwillandIntangibleAssetsDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#SummaryofSignificantAccountingPoliciesGoodwillandIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/SummaryofSignificantAccountingPoliciesGoodwillandIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_7478ed0a-aa03-4449-b366-c6f9506335fb" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_b95aebb0-0640-48e8-a8e6-eed8da0c0097" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_7478ed0a-aa03-4449-b366-c6f9506335fb" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_b95aebb0-0640-48e8-a8e6-eed8da0c0097" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0298f64d-2be0-4b9c-94c3-43e676480fc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_b95aebb0-0640-48e8-a8e6-eed8da0c0097" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0298f64d-2be0-4b9c-94c3-43e676480fc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0298f64d-2be0-4b9c-94c3-43e676480fc7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0298f64d-2be0-4b9c-94c3-43e676480fc7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0298f64d-2be0-4b9c-94c3-43e676480fc7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faab34eb-cc56-48b2-831f-58cf39acc6b5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_0298f64d-2be0-4b9c-94c3-43e676480fc7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faab34eb-cc56-48b2-831f-58cf39acc6b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_521eb511-6a85-43ee-979b-56b78b17593c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faab34eb-cc56-48b2-831f-58cf39acc6b5" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_521eb511-6a85-43ee-979b-56b78b17593c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_25c5ea61-56f1-4589-8477-b8c4774065b4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faab34eb-cc56-48b2-831f-58cf39acc6b5" xlink:to="loc_us-gaap_CustomerRelationshipsMember_25c5ea61-56f1-4589-8477-b8c4774065b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_f4080b5e-f7e2-49b0-b9f6-41aec081ca6a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_7478ed0a-aa03-4449-b366-c6f9506335fb" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_f4080b5e-f7e2-49b0-b9f6-41aec081ca6a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/RevenueAdditionalInformationDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#RevenueAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/RevenueAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_f8755681-e4d4-4146-be91-cdfb3ac3a460" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_f8755681-e4d4-4146-be91-cdfb3ac3a460" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_2563d764-40c8-4630-8686-94f98ccc2460" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:to="loc_srt_ProductOrServiceAxis_2563d764-40c8-4630-8686-94f98ccc2460" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_2563d764-40c8-4630-8686-94f98ccc2460_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_2563d764-40c8-4630-8686-94f98ccc2460" xlink:to="loc_srt_ProductsAndServicesDomain_2563d764-40c8-4630-8686-94f98ccc2460_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_2563d764-40c8-4630-8686-94f98ccc2460" xlink:to="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SoftwareAsAServiceMember_e7f4a934-54a5-4597-8fea-03d57444954e" xlink:href="cvlt-20250630.xsd#cvlt_SoftwareAsAServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:to="loc_cvlt_SoftwareAsAServiceMember_e7f4a934-54a5-4597-8fea-03d57444954e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SubscriptionMember_5997ab50-4e49-400a-9d25-49a258ac1e3d" xlink:href="cvlt-20250630.xsd#cvlt_SubscriptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:to="loc_cvlt_SubscriptionMember_5997ab50-4e49-400a-9d25-49a258ac1e3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CustomerSupportServiceMember_a344f33c-2dda-453e-922f-acb6a6c7a3aa" xlink:href="cvlt-20250630.xsd#cvlt_CustomerSupportServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:to="loc_cvlt_CustomerSupportServiceMember_a344f33c-2dda-453e-922f-acb6a6c7a3aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceOtherMember_da8584e1-6b1f-43fd-8366-8a52ba119cbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:to="loc_us-gaap_ServiceOtherMember_da8584e1-6b1f-43fd-8366-8a52ba119cbc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_93d8404b-9d38-4653-af53-ec1acc428ce7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:to="loc_srt_RangeAxis_93d8404b-9d38-4653-af53-ec1acc428ce7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_93d8404b-9d38-4653-af53-ec1acc428ce7_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_93d8404b-9d38-4653-af53-ec1acc428ce7" xlink:to="loc_srt_RangeMember_93d8404b-9d38-4653-af53-ec1acc428ce7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5c1b5e12-317d-4fed-b542-02b47d38c039" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_93d8404b-9d38-4653-af53-ec1acc428ce7" xlink:to="loc_srt_RangeMember_5c1b5e12-317d-4fed-b542-02b47d38c039" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_b3543f4e-8087-4817-9e9c-5f864a8d4758" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5c1b5e12-317d-4fed-b542-02b47d38c039" xlink:to="loc_srt_MinimumMember_b3543f4e-8087-4817-9e9c-5f864a8d4758" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_a6bdd08d-f297-456f-9ae4-af30e8fa7549" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5c1b5e12-317d-4fed-b542-02b47d38c039" xlink:to="loc_srt_MaximumMember_a6bdd08d-f297-456f-9ae4-af30e8fa7549" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_53f40209-e407-4645-bd3e-0c9f61bc8277" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:to="loc_srt_StatementScenarioAxis_53f40209-e407-4645-bd3e-0c9f61bc8277" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_53f40209-e407-4645-bd3e-0c9f61bc8277_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_53f40209-e407-4645-bd3e-0c9f61bc8277" xlink:to="loc_srt_ScenarioUnspecifiedDomain_53f40209-e407-4645-bd3e-0c9f61bc8277_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_149bc660-f2e9-4596-a9d9-34a52c94e466" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_53f40209-e407-4645-bd3e-0c9f61bc8277" xlink:to="loc_srt_ScenarioUnspecifiedDomain_149bc660-f2e9-4596-a9d9-34a52c94e466" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_356e4cae-caf5-4bd4-bf49-815b383bb3e0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_149bc660-f2e9-4596-a9d9-34a52c94e466" xlink:to="loc_srt_ScenarioForecastMember_356e4cae-caf5-4bd4-bf49-815b383bb3e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SubscriptionArrangementTerm_6c54ff1a-d8bb-4c1f-a3d5-c09579d885e3" xlink:href="cvlt-20250630.xsd#cvlt_SubscriptionArrangementTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_cvlt_SubscriptionArrangementTerm_6c54ff1a-d8bb-4c1f-a3d5-c09579d885e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CustomerSupportArrangementTerm_82dcf1cc-621e-4f6d-9469-5c2cdeab4779" xlink:href="cvlt-20250630.xsd#cvlt_CustomerSupportArrangementTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_cvlt_CustomerSupportArrangementTerm_82dcf1cc-621e-4f6d-9469-5c2cdeab4779" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_a9a4800d-522f-4cd0-ae65-aa0dec29150d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_a9a4800d-522f-4cd0-ae65-aa0dec29150d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_30549c3e-225d-4d41-913d-4c0defcf48df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_30549c3e-225d-4d41-913d-4c0defcf48df" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_bbba559d-d610-4a0a-8a33-14312bf3cf0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_bbba559d-d610-4a0a-8a33-14312bf3cf0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_RevenueRemainingPerformanceObligationPercentageRecognized_6b4f7f3d-9c67-45f6-83e3-dca9165c2e51" xlink:href="cvlt-20250630.xsd#cvlt_RevenueRemainingPerformanceObligationPercentageRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_cvlt_RevenueRemainingPerformanceObligationPercentageRecognized_6b4f7f3d-9c67-45f6-83e3-dca9165c2e51" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_1df483ac-8e4c-4364-92b6-e2194c3b2113" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_1df483ac-8e4c-4364-92b6-e2194c3b2113" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/RevenueAdditionalInformationDetails_1" xlink:type="simple" xlink:href="cvlt-20250630.xsd#RevenueAdditionalInformationDetails_1"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/RevenueAdditionalInformationDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_2563d764-40c8-4630-8686-94f98ccc2460" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:to="loc_srt_ProductOrServiceAxis_2563d764-40c8-4630-8686-94f98ccc2460" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_2563d764-40c8-4630-8686-94f98ccc2460_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_2563d764-40c8-4630-8686-94f98ccc2460" xlink:to="loc_srt_ProductsAndServicesDomain_2563d764-40c8-4630-8686-94f98ccc2460_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_2563d764-40c8-4630-8686-94f98ccc2460" xlink:to="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SoftwareAsAServiceMember_e7f4a934-54a5-4597-8fea-03d57444954e" xlink:href="cvlt-20250630.xsd#cvlt_SoftwareAsAServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:to="loc_cvlt_SoftwareAsAServiceMember_e7f4a934-54a5-4597-8fea-03d57444954e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SubscriptionMember_5997ab50-4e49-400a-9d25-49a258ac1e3d" xlink:href="cvlt-20250630.xsd#cvlt_SubscriptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:to="loc_cvlt_SubscriptionMember_5997ab50-4e49-400a-9d25-49a258ac1e3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CustomerSupportServiceMember_a344f33c-2dda-453e-922f-acb6a6c7a3aa" xlink:href="cvlt-20250630.xsd#cvlt_CustomerSupportServiceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:to="loc_cvlt_CustomerSupportServiceMember_a344f33c-2dda-453e-922f-acb6a6c7a3aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceOtherMember_da8584e1-6b1f-43fd-8366-8a52ba119cbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ServiceOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_302dbab8-e768-4375-94ff-4b83eff783d6" xlink:to="loc_us-gaap_ServiceOtherMember_da8584e1-6b1f-43fd-8366-8a52ba119cbc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_93d8404b-9d38-4653-af53-ec1acc428ce7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:to="loc_srt_RangeAxis_93d8404b-9d38-4653-af53-ec1acc428ce7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_93d8404b-9d38-4653-af53-ec1acc428ce7_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_93d8404b-9d38-4653-af53-ec1acc428ce7" xlink:to="loc_srt_RangeMember_93d8404b-9d38-4653-af53-ec1acc428ce7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5c1b5e12-317d-4fed-b542-02b47d38c039" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_93d8404b-9d38-4653-af53-ec1acc428ce7" xlink:to="loc_srt_RangeMember_5c1b5e12-317d-4fed-b542-02b47d38c039" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_b3543f4e-8087-4817-9e9c-5f864a8d4758" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5c1b5e12-317d-4fed-b542-02b47d38c039" xlink:to="loc_srt_MinimumMember_b3543f4e-8087-4817-9e9c-5f864a8d4758" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_a6bdd08d-f297-456f-9ae4-af30e8fa7549" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5c1b5e12-317d-4fed-b542-02b47d38c039" xlink:to="loc_srt_MaximumMember_a6bdd08d-f297-456f-9ae4-af30e8fa7549" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_53f40209-e407-4645-bd3e-0c9f61bc8277" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_d027e157-1d7c-4146-a2a6-243691b120b0" xlink:to="loc_srt_StatementScenarioAxis_53f40209-e407-4645-bd3e-0c9f61bc8277" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_53f40209-e407-4645-bd3e-0c9f61bc8277_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_53f40209-e407-4645-bd3e-0c9f61bc8277" xlink:to="loc_srt_ScenarioUnspecifiedDomain_53f40209-e407-4645-bd3e-0c9f61bc8277_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_149bc660-f2e9-4596-a9d9-34a52c94e466" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_53f40209-e407-4645-bd3e-0c9f61bc8277" xlink:to="loc_srt_ScenarioUnspecifiedDomain_149bc660-f2e9-4596-a9d9-34a52c94e466" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_356e4cae-caf5-4bd4-bf49-815b383bb3e0" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_149bc660-f2e9-4596-a9d9-34a52c94e466" xlink:to="loc_srt_ScenarioForecastMember_356e4cae-caf5-4bd4-bf49-815b383bb3e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SubscriptionArrangementTerm_6c54ff1a-d8bb-4c1f-a3d5-c09579d885e3" xlink:href="cvlt-20250630.xsd#cvlt_SubscriptionArrangementTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_cvlt_SubscriptionArrangementTerm_6c54ff1a-d8bb-4c1f-a3d5-c09579d885e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CustomerSupportArrangementTerm_82dcf1cc-621e-4f6d-9469-5c2cdeab4779" xlink:href="cvlt-20250630.xsd#cvlt_CustomerSupportArrangementTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_cvlt_CustomerSupportArrangementTerm_82dcf1cc-621e-4f6d-9469-5c2cdeab4779" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_a9a4800d-522f-4cd0-ae65-aa0dec29150d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_a9a4800d-522f-4cd0-ae65-aa0dec29150d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_30549c3e-225d-4d41-913d-4c0defcf48df" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationPercentage_30549c3e-225d-4d41-913d-4c0defcf48df" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_bbba559d-d610-4a0a-8a33-14312bf3cf0b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_bbba559d-d610-4a0a-8a33-14312bf3cf0b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_RevenueRemainingPerformanceObligationPercentageRecognized_6b4f7f3d-9c67-45f6-83e3-dca9165c2e51" xlink:href="cvlt-20250630.xsd#cvlt_RevenueRemainingPerformanceObligationPercentageRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_cvlt_RevenueRemainingPerformanceObligationPercentageRecognized_6b4f7f3d-9c67-45f6-83e3-dca9165c2e51" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_1df483ac-8e4c-4364-92b6-e2194c3b2113" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_27d25285-35e3-455f-9cb0-a5136b87b1e7" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_1df483ac-8e4c-4364-92b6-e2194c3b2113" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/RevenuePerformanceObligationsDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#RevenuePerformanceObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/RevenuePerformanceObligationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_a9c41196-bbdb-47be-b5f3-1c9d1cd9d8ea" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a13007a1-9c0d-4370-b5e5-820511313dab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_a9c41196-bbdb-47be-b5f3-1c9d1cd9d8ea" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a13007a1-9c0d-4370-b5e5-820511313dab" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_4f61dcd5-0cd2-4e29-8edf-0d600d9fac32" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a13007a1-9c0d-4370-b5e5-820511313dab" xlink:to="loc_srt_ProductOrServiceAxis_4f61dcd5-0cd2-4e29-8edf-0d600d9fac32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_4f61dcd5-0cd2-4e29-8edf-0d600d9fac32_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_4f61dcd5-0cd2-4e29-8edf-0d600d9fac32" xlink:to="loc_srt_ProductsAndServicesDomain_4f61dcd5-0cd2-4e29-8edf-0d600d9fac32_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_4f69fa5d-849a-48b9-9f6f-bdb6d58e5c4e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_4f61dcd5-0cd2-4e29-8edf-0d600d9fac32" xlink:to="loc_srt_ProductsAndServicesDomain_4f69fa5d-849a-48b9-9f6f-bdb6d58e5c4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_TermBasedSoftwareLicensesMember_c97034f3-e4be-4087-bbb2-2374e2e0033d" xlink:href="cvlt-20250630.xsd#cvlt_TermBasedSoftwareLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4f69fa5d-849a-48b9-9f6f-bdb6d58e5c4e" xlink:to="loc_cvlt_TermBasedSoftwareLicensesMember_c97034f3-e4be-4087-bbb2-2374e2e0033d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_PerpetualSoftwareLicensesMember_ee7a3709-01e0-4e69-b881-7c9954c9001b" xlink:href="cvlt-20250630.xsd#cvlt_PerpetualSoftwareLicensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4f69fa5d-849a-48b9-9f6f-bdb6d58e5c4e" xlink:to="loc_cvlt_PerpetualSoftwareLicensesMember_ee7a3709-01e0-4e69-b881-7c9954c9001b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ProfessionalServicesOtherMember_4b25c721-3ae4-4f4b-9d34-0c70465272ba" xlink:href="cvlt-20250630.xsd#cvlt_ProfessionalServicesOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_4f69fa5d-849a-48b9-9f6f-bdb6d58e5c4e" xlink:to="loc_cvlt_ProfessionalServicesOtherMember_4b25c721-3ae4-4f4b-9d34-0c70465272ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_RevenuePerformanceObligationDescriptionOfPaymentTermsPeriod_2ae935c9-9589-4a90-a7a1-d1e70ff41c95" xlink:href="cvlt-20250630.xsd#cvlt_RevenuePerformanceObligationDescriptionOfPaymentTermsPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_a9c41196-bbdb-47be-b5f3-1c9d1cd9d8ea" xlink:to="loc_cvlt_RevenuePerformanceObligationDescriptionOfPaymentTermsPeriod_2ae935c9-9589-4a90-a7a1-d1e70ff41c95" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/RevenueDisaggregationofRevenuesDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#RevenueDisaggregationofRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/RevenueDisaggregationofRevenuesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_e903382d-6222-45e2-8286-71c4215113c2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_72ea7c9c-2959-49fe-bffe-3e35f39c374e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_e903382d-6222-45e2-8286-71c4215113c2" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_72ea7c9c-2959-49fe-bffe-3e35f39c374e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_cc7d1174-a40a-4616-b197-5dce54506ce9" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_72ea7c9c-2959-49fe-bffe-3e35f39c374e" xlink:to="loc_srt_StatementGeographicalAxis_cc7d1174-a40a-4616-b197-5dce54506ce9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_cc7d1174-a40a-4616-b197-5dce54506ce9_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_cc7d1174-a40a-4616-b197-5dce54506ce9" xlink:to="loc_srt_SegmentGeographicalDomain_cc7d1174-a40a-4616-b197-5dce54506ce9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_b0ea866e-e097-430a-88b0-404bb4b3d4fd" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_cc7d1174-a40a-4616-b197-5dce54506ce9" xlink:to="loc_srt_SegmentGeographicalDomain_b0ea866e-e097-430a-88b0-404bb4b3d4fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AmericasMember_0a3feb38-e3c6-45e9-be84-a62a9ae5699e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_AmericasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_b0ea866e-e097-430a-88b0-404bb4b3d4fd" xlink:to="loc_srt_AmericasMember_0a3feb38-e3c6-45e9-be84-a62a9ae5699e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_InternationalMember_86e261f1-4c79-444a-b919-a6fce5ead158" xlink:href="cvlt-20250630.xsd#cvlt_InternationalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_b0ea866e-e097-430a-88b0-404bb4b3d4fd" xlink:to="loc_cvlt_InternationalMember_86e261f1-4c79-444a-b919-a6fce5ead158" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d9b647a8-6087-4687-85b8-f1462990efae" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_e903382d-6222-45e2-8286-71c4215113c2" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_d9b647a8-6087-4687-85b8-f1462990efae" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/RevenueOpeningandClosingBalancesofAccountsReceivablesUnbilledReceivablesandDeferredRevenuesDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#RevenueOpeningandClosingBalancesofAccountsReceivablesUnbilledReceivablesandDeferredRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/RevenueOpeningandClosingBalancesofAccountsReceivablesUnbilledReceivablesandDeferredRevenuesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f3e0be91-74c2-4243-a122-46cd6915cd71" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_6f3cb06f-435d-4ac6-a9d3-7345d68e7709" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f3e0be91-74c2-4243-a122-46cd6915cd71" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_6f3cb06f-435d-4ac6-a9d3-7345d68e7709" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_9db850b8-097b-4c79-a380-2fb4defaea73" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_6f3cb06f-435d-4ac6-a9d3-7345d68e7709" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_9db850b8-097b-4c79-a380-2fb4defaea73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_9db850b8-097b-4c79-a380-2fb4defaea73_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_9db850b8-097b-4c79-a380-2fb4defaea73" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_9db850b8-097b-4c79-a380-2fb4defaea73_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_103867d5-5cec-48b0-b6c0-3ace3ca41ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_9db850b8-097b-4c79-a380-2fb4defaea73" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_103867d5-5cec-48b0-b6c0-3ace3ca41ef1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeAccountsReceivableMember_499915d2-267e-4422-9659-e405520a7763" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_TradeAccountsReceivableMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_103867d5-5cec-48b0-b6c0-3ace3ca41ef1" xlink:to="loc_us-gaap_TradeAccountsReceivableMember_499915d2-267e-4422-9659-e405520a7763" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMember_ed40fe26-f095-4734-bc92-35d551983f1c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_103867d5-5cec-48b0-b6c0-3ace3ca41ef1" xlink:to="loc_us-gaap_OtherAssetsMember_ed40fe26-f095-4734-bc92-35d551983f1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_DeferredRevenueCurrentMember_1ca7e8be-683e-4c16-84bd-dd924b6c3577" xlink:href="cvlt-20250630.xsd#cvlt_DeferredRevenueCurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_103867d5-5cec-48b0-b6c0-3ace3ca41ef1" xlink:to="loc_cvlt_DeferredRevenueCurrentMember_1ca7e8be-683e-4c16-84bd-dd924b6c3577" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_DeferredRevenueNoncurrentMember_11b20b26-20e8-45ad-bf25-e88bc5269765" xlink:href="cvlt-20250630.xsd#cvlt_DeferredRevenueNoncurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_103867d5-5cec-48b0-b6c0-3ace3ca41ef1" xlink:to="loc_cvlt_DeferredRevenueNoncurrentMember_11b20b26-20e8-45ad-bf25-e88bc5269765" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_AccountsReceivableRollForward_54780579-0050-43e4-9fde-e1b5bc15ecd1" xlink:href="cvlt-20250630.xsd#cvlt_AccountsReceivableRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f3e0be91-74c2-4243-a122-46cd6915cd71" xlink:to="loc_cvlt_AccountsReceivableRollForward_54780579-0050-43e4-9fde-e1b5bc15ecd1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_b51fd717-d99d-47e1-88df-8ddf888c5583" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_AccountsReceivableRollForward_54780579-0050-43e4-9fde-e1b5bc15ecd1" xlink:to="loc_us-gaap_AccountsReceivableNet_b51fd717-d99d-47e1-88df-8ddf888c5583" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_9ab32816-1484-453f-aa7c-8c854113a68d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_AccountsReceivableRollForward_54780579-0050-43e4-9fde-e1b5bc15ecd1" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_9ab32816-1484-453f-aa7c-8c854113a68d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNet_a3f18917-6bce-46f7-bb7f-94d552394809" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountsReceivableNet"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ContractWithCustomerAssetNetCurrentRollForward_ebcb1b24-1948-4956-a78b-5ce55c16129f" xlink:href="cvlt-20250630.xsd#cvlt_ContractWithCustomerAssetNetCurrentRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f3e0be91-74c2-4243-a122-46cd6915cd71" xlink:to="loc_cvlt_ContractWithCustomerAssetNetCurrentRollForward_ebcb1b24-1948-4956-a78b-5ce55c16129f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_e4d457d1-3203-4451-a06e-10a1610bd634" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ContractWithCustomerAssetNetCurrentRollForward_ebcb1b24-1948-4956-a78b-5ce55c16129f" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetCurrent_e4d457d1-3203-4451-a06e-10a1610bd634" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ContractWithCustomerAssetNetCurrentIncreaseDecrease_59f87d7f-20de-4f99-833c-8cef7834a3dd" xlink:href="cvlt-20250630.xsd#cvlt_ContractWithCustomerAssetNetCurrentIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ContractWithCustomerAssetNetCurrentRollForward_ebcb1b24-1948-4956-a78b-5ce55c16129f" xlink:to="loc_cvlt_ContractWithCustomerAssetNetCurrentIncreaseDecrease_59f87d7f-20de-4f99-833c-8cef7834a3dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetCurrent_f898eece-46a3-48ec-b63f-0f4994643dbc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerAssetNetCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ContractWithCustomerAssetNetNoncurrentRollForward_e3919ee2-4a2c-4766-bf2b-4ec97e8cccd6" xlink:href="cvlt-20250630.xsd#cvlt_ContractWithCustomerAssetNetNoncurrentRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f3e0be91-74c2-4243-a122-46cd6915cd71" xlink:to="loc_cvlt_ContractWithCustomerAssetNetNoncurrentRollForward_e3919ee2-4a2c-4766-bf2b-4ec97e8cccd6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetNoncurrent_c68b38bc-0570-41b9-9b56-d2c5ed34b198" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerAssetNetNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ContractWithCustomerAssetNetNoncurrentRollForward_e3919ee2-4a2c-4766-bf2b-4ec97e8cccd6" xlink:to="loc_us-gaap_ContractWithCustomerAssetNetNoncurrent_c68b38bc-0570-41b9-9b56-d2c5ed34b198" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ContractWithCustomerAssetNetNoncurrentIncreaseDecrease_83abeac7-a9c0-4741-977b-6d636b5f8183" xlink:href="cvlt-20250630.xsd#cvlt_ContractWithCustomerAssetNetNoncurrentIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ContractWithCustomerAssetNetNoncurrentRollForward_e3919ee2-4a2c-4766-bf2b-4ec97e8cccd6" xlink:to="loc_cvlt_ContractWithCustomerAssetNetNoncurrentIncreaseDecrease_83abeac7-a9c0-4741-977b-6d636b5f8183" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerAssetNetNoncurrent_73c4c860-9103-4ae5-9f25-4a181fd06360" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerAssetNetNoncurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ContractWithCustomerLiabilityCurrentRollForward_d883ae57-2815-4c69-8b4a-28d1cca5d33c" xlink:href="cvlt-20250630.xsd#cvlt_ContractWithCustomerLiabilityCurrentRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f3e0be91-74c2-4243-a122-46cd6915cd71" xlink:to="loc_cvlt_ContractWithCustomerLiabilityCurrentRollForward_d883ae57-2815-4c69-8b4a-28d1cca5d33c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_728fc324-3719-495a-8f11-cb8e6c27bdfa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ContractWithCustomerLiabilityCurrentRollForward_d883ae57-2815-4c69-8b4a-28d1cca5d33c" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityCurrent_728fc324-3719-495a-8f11-cb8e6c27bdfa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ContractWithCustomerLiabilityCurrentIncreaseDecrease_a508e627-3f95-4ddf-a68c-8a3239273c26" xlink:href="cvlt-20250630.xsd#cvlt_ContractWithCustomerLiabilityCurrentIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ContractWithCustomerLiabilityCurrentRollForward_d883ae57-2815-4c69-8b4a-28d1cca5d33c" xlink:to="loc_cvlt_ContractWithCustomerLiabilityCurrentIncreaseDecrease_a508e627-3f95-4ddf-a68c-8a3239273c26" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityCurrent_f5397821-85c9-453e-b050-7288a4849e05" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityCurrent"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ContractWithCustomerLiabilityNoncurrentRollForward_e6176486-a968-41e8-abb6-6af7322e463d" xlink:href="cvlt-20250630.xsd#cvlt_ContractWithCustomerLiabilityNoncurrentRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_f3e0be91-74c2-4243-a122-46cd6915cd71" xlink:to="loc_cvlt_ContractWithCustomerLiabilityNoncurrentRollForward_e6176486-a968-41e8-abb6-6af7322e463d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_29a1200c-9f03-4ee6-8352-142c62f28e04" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ContractWithCustomerLiabilityNoncurrentRollForward_e6176486-a968-41e8-abb6-6af7322e463d" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_29a1200c-9f03-4ee6-8352-142c62f28e04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ContractWithCustomerLiabilityNoncurrentIncreaseDecrease_2ea78155-e262-49db-b2be-7bf86835ee88" xlink:href="cvlt-20250630.xsd#cvlt_ContractWithCustomerLiabilityNoncurrentIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_cvlt_ContractWithCustomerLiabilityNoncurrentRollForward_e6176486-a968-41e8-abb6-6af7322e463d" xlink:to="loc_cvlt_ContractWithCustomerLiabilityNoncurrentIncreaseDecrease_2ea78155-e262-49db-b2be-7bf86835ee88" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_a204dd94-2440-401b-a7e5-9a7d4b9fb9ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/SaleandLeasebackTransactionDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#SaleandLeasebackTransactionDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/SaleandLeasebackTransactionDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_63455edd-88f8-4e06-aaa6-8ab1ef5831a9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_4b010bfb-4a2e-4765-8cf4-6e7f5d0727e0" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_63455edd-88f8-4e06-aaa6-8ab1ef5831a9" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_4b010bfb-4a2e-4765-8cf4-6e7f5d0727e0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationAxis_5ba3e794-c864-4230-b355-c0253c3ac0db" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_4b010bfb-4a2e-4765-8cf4-6e7f5d0727e0" xlink:to="loc_us-gaap_DisposalGroupClassificationAxis_5ba3e794-c864-4230-b355-c0253c3ac0db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_5ba3e794-c864-4230-b355-c0253c3ac0db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_5ba3e794-c864-4230-b355-c0253c3ac0db" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_5ba3e794-c864-4230-b355-c0253c3ac0db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupClassificationDomain_7cc9a541-7151-467d-8825-27b305357494" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DisposalGroupClassificationAxis_5ba3e794-c864-4230-b355-c0253c3ac0db" xlink:to="loc_us-gaap_DisposalGroupClassificationDomain_7cc9a541-7151-467d-8825-27b305357494" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_9ddc86f1-ab48-45df-95b6-e1536c75c76d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupClassificationDomain_7cc9a541-7151-467d-8825-27b305357494" xlink:to="loc_us-gaap_DisposalGroupDisposedOfBySaleNotDiscontinuedOperationsMember_9ddc86f1-ab48-45df-95b6-e1536c75c76d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_c021501a-ee3c-42f0-8675-d32db964bd7e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_4b010bfb-4a2e-4765-8cf4-6e7f5d0727e0" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_c021501a-ee3c-42f0-8675-d32db964bd7e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_c021501a-ee3c-42f0-8675-d32db964bd7e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_c021501a-ee3c-42f0-8675-d32db964bd7e" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_c021501a-ee3c-42f0-8675-d32db964bd7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a3ce3620-3ada-424d-b3de-95e5e2b010d2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_c021501a-ee3c-42f0-8675-d32db964bd7e" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a3ce3620-3ada-424d-b3de-95e5e2b010d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CorporateHeadquartersInTintonFallsNJMember_828fa0bc-d881-41fd-93de-a7ef2506c997" xlink:href="cvlt-20250630.xsd#cvlt_CorporateHeadquartersInTintonFallsNJMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_a3ce3620-3ada-424d-b3de-95e5e2b010d2" xlink:to="loc_cvlt_CorporateHeadquartersInTintonFallsNJMember_828fa0bc-d881-41fd-93de-a7ef2506c997" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleLeasebackTransactionDescriptionAxis_3b6bbe90-6bf9-49c6-9803-5bbfd8e96674" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleLeasebackTransactionDescriptionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_4b010bfb-4a2e-4765-8cf4-6e7f5d0727e0" xlink:to="loc_us-gaap_SaleLeasebackTransactionDescriptionAxis_3b6bbe90-6bf9-49c6-9803-5bbfd8e96674" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleLeasebackTransactionNameDomain_3b6bbe90-6bf9-49c6-9803-5bbfd8e96674_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleLeasebackTransactionNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SaleLeasebackTransactionDescriptionAxis_3b6bbe90-6bf9-49c6-9803-5bbfd8e96674" xlink:to="loc_us-gaap_SaleLeasebackTransactionNameDomain_3b6bbe90-6bf9-49c6-9803-5bbfd8e96674_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleLeasebackTransactionNameDomain_b6e4ec49-3e6b-4d38-bf0b-60c5c7a33fb9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleLeasebackTransactionNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SaleLeasebackTransactionDescriptionAxis_3b6bbe90-6bf9-49c6-9803-5bbfd8e96674" xlink:to="loc_us-gaap_SaleLeasebackTransactionNameDomain_b6e4ec49-3e6b-4d38-bf0b-60c5c7a33fb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_CorporateHeadquartersInTintonFallsNJMember_5c90b065-660b-4130-b9fe-ec5620e59566" xlink:href="cvlt-20250630.xsd#cvlt_CorporateHeadquartersInTintonFallsNJMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleLeasebackTransactionNameDomain_b6e4ec49-3e6b-4d38-bf0b-60c5c7a33fb9" xlink:to="loc_cvlt_CorporateHeadquartersInTintonFallsNJMember_5c90b065-660b-4130-b9fe-ec5620e59566" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_24dd6810-74f1-4cee-b1e8-0b0bdfd60d08" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_63455edd-88f8-4e06-aaa6-8ab1ef5831a9" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_24dd6810-74f1-4cee-b1e8-0b0bdfd60d08" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleLeasebackTransactionLeaseTerm_81467889-9984-4091-b3a5-6ee2019230bf" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleLeasebackTransactionLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_63455edd-88f8-4e06-aaa6-8ab1ef5831a9" xlink:to="loc_us-gaap_SaleLeasebackTransactionLeaseTerm_81467889-9984-4091-b3a5-6ee2019230bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OffMarketLeaseUnfavorable_9083f6a3-e042-4e6e-a104-0b725858088e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OffMarketLeaseUnfavorable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_63455edd-88f8-4e06-aaa6-8ab1ef5831a9" xlink:to="loc_us-gaap_OffMarketLeaseUnfavorable_9083f6a3-e042-4e6e-a104-0b725858088e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SaleAndLeasebackTransactionGainLossNet_869f82e3-9bfc-44e2-a09c-5b155befb227" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SaleAndLeasebackTransactionGainLossNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_63455edd-88f8-4e06-aaa6-8ab1ef5831a9" xlink:to="loc_us-gaap_SaleAndLeasebackTransactionGainLossNet_869f82e3-9bfc-44e2-a09c-5b155befb227" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_42b816b2-c61b-4568-b748-2375798e9bb5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_63455edd-88f8-4e06-aaa6-8ab1ef5831a9" xlink:to="loc_us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_42b816b2-c61b-4568-b748-2375798e9bb5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseDiscountRate_b88f8648-fc1c-46aa-aef9-41dfc8d8c036" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_63455edd-88f8-4e06-aaa6-8ab1ef5831a9" xlink:to="loc_us-gaap_LesseeOperatingLeaseDiscountRate_b88f8648-fc1c-46aa-aef9-41dfc8d8c036" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/StockPlansStockBasedCompensationExpenseDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#StockPlansStockBasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/StockPlansStockBasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_18304603-1e90-45eb-83e2-bf14a4a28191" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_eb456d81-1ff2-4458-a81f-f0b83aa0aba5" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_18304603-1e90-45eb-83e2-bf14a4a28191" xlink:to="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_eb456d81-1ff2-4458-a81f-f0b83aa0aba5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_26601aea-f495-40cd-9017-91bdbc7e69c1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_eb456d81-1ff2-4458-a81f-f0b83aa0aba5" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_26601aea-f495-40cd-9017-91bdbc7e69c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_26601aea-f495-40cd-9017-91bdbc7e69c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_26601aea-f495-40cd-9017-91bdbc7e69c1" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_26601aea-f495-40cd-9017-91bdbc7e69c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_cbd8d810-7459-4046-ac18-31ca65dcda6c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_26601aea-f495-40cd-9017-91bdbc7e69c1" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_cbd8d810-7459-4046-ac18-31ca65dcda6c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_374ec923-8a93-4d61-b8f8-a48f6590ac3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_cbd8d810-7459-4046-ac18-31ca65dcda6c" xlink:to="loc_us-gaap_CostOfSalesMember_374ec923-8a93-4d61-b8f8-a48f6590ac3d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingAndMarketingExpenseMember_7d2c933d-6a8f-48dd-a939-6959eb124dc3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SellingAndMarketingExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_cbd8d810-7459-4046-ac18-31ca65dcda6c" xlink:to="loc_us-gaap_SellingAndMarketingExpenseMember_7d2c933d-6a8f-48dd-a939-6959eb124dc3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_2daec36e-2c06-4514-9a4d-b74a96774987" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ResearchAndDevelopmentExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_cbd8d810-7459-4046-ac18-31ca65dcda6c" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_2daec36e-2c06-4514-9a4d-b74a96774987" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_18a19873-2acf-4091-b7d2-558e5dd8abf4" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_GeneralAndAdministrativeExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_cbd8d810-7459-4046-ac18-31ca65dcda6c" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_18a19873-2acf-4091-b7d2-558e5dd8abf4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringChargesMember_48021616-e004-4b28-bd3b-6decac3f8315" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringChargesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_cbd8d810-7459-4046-ac18-31ca65dcda6c" xlink:to="loc_us-gaap_RestructuringChargesMember_48021616-e004-4b28-bd3b-6decac3f8315" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_e56f650f-9879-4b21-887b-eae4ec295416" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_18304603-1e90-45eb-83e2-bf14a4a28191" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_e56f650f-9879-4b21-887b-eae4ec295416" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/StockPlansAdditionalInformationDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#StockPlansAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/StockPlansAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_70364bec-c6a7-47f7-9a7e-8758fd313be8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_70364bec-c6a7-47f7-9a7e-8758fd313be8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_199fcb83-5912-4437-8748-79f26cd48dc6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_70364bec-c6a7-47f7-9a7e-8758fd313be8" xlink:to="loc_us-gaap_AwardTypeAxis_199fcb83-5912-4437-8748-79f26cd48dc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_199fcb83-5912-4437-8748-79f26cd48dc6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_199fcb83-5912-4437-8748-79f26cd48dc6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_199fcb83-5912-4437-8748-79f26cd48dc6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a922c7c1-1c4e-4b8c-abb9-064c14c33fc7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_199fcb83-5912-4437-8748-79f26cd48dc6" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a922c7c1-1c4e-4b8c-abb9-064c14c33fc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_185031c6-5f6a-4ee6-9b86-3aafba4783fa" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a922c7c1-1c4e-4b8c-abb9-064c14c33fc7" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_185031c6-5f6a-4ee6-9b86-3aafba4783fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_PerformanceStockUnitsMember_23d1f37f-abd4-4432-9ff8-47e6c709663c" xlink:href="cvlt-20250630.xsd#cvlt_PerformanceStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a922c7c1-1c4e-4b8c-abb9-064c14c33fc7" xlink:to="loc_cvlt_PerformanceStockUnitsMember_23d1f37f-abd4-4432-9ff8-47e6c709663c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_d53dd1db-99e9-47ec-a15d-61bcf389e9b1" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a922c7c1-1c4e-4b8c-abb9-064c14c33fc7" xlink:to="loc_us-gaap_PerformanceSharesMember_d53dd1db-99e9-47ec-a15d-61bcf389e9b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_2c3286a6-8166-4cbe-8696-831ae75c5c7e" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_70364bec-c6a7-47f7-9a7e-8758fd313be8" xlink:to="loc_srt_RangeAxis_2c3286a6-8166-4cbe-8696-831ae75c5c7e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_2c3286a6-8166-4cbe-8696-831ae75c5c7e_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_2c3286a6-8166-4cbe-8696-831ae75c5c7e" xlink:to="loc_srt_RangeMember_2c3286a6-8166-4cbe-8696-831ae75c5c7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_0549ce1d-819f-4568-bea4-a0d1b752103c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_2c3286a6-8166-4cbe-8696-831ae75c5c7e" xlink:to="loc_srt_RangeMember_0549ce1d-819f-4568-bea4-a0d1b752103c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_13df5faf-c456-4be0-8ea0-e89fe6e63fc7" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0549ce1d-819f-4568-bea4-a0d1b752103c" xlink:to="loc_srt_MinimumMember_13df5faf-c456-4be0-8ea0-e89fe6e63fc7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_275801d7-ac35-42ed-b09a-1aebfc96ea21" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0549ce1d-819f-4568-bea4-a0d1b752103c" xlink:to="loc_srt_MaximumMember_275801d7-ac35-42ed-b09a-1aebfc96ea21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_b2c1f686-351b-4351-9053-4d2c31727012" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_b2c1f686-351b-4351-9053-4d2c31727012" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_340812b0-3944-4619-b5e4-00d9ecc3b76b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_340812b0-3944-4619-b5e4-00d9ecc3b76b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_8ab06ede-c132-4ba6-9a56-f148b335a564" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_8ab06ede-c132-4ba6-9a56-f148b335a564" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_e7eb7a5f-91fb-487a-ac92-fe273d074489" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_e7eb7a5f-91fb-487a-ac92-fe273d074489" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_f11f14bc-1fa1-45e5-bef2-58fe78944da6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_f11f14bc-1fa1-45e5-bef2-58fe78944da6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPotentialToVestPercent_59ad60b2-6ea8-417f-8320-e9b4c16f6c57" xlink:href="cvlt-20250630.xsd#cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPotentialToVestPercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPotentialToVestPercent_59ad60b2-6ea8-417f-8320-e9b4c16f6c57" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPotentialToVestShares_4c78a395-f0c1-4434-8d79-f9760d25c8b4" xlink:href="cvlt-20250630.xsd#cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPotentialToVestShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPotentialToVestShares_4c78a395-f0c1-4434-8d79-f9760d25c8b4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAnnualVestingTranches_f136cd00-63ce-4753-ace1-ce81f099f1da" xlink:href="cvlt-20250630.xsd#cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAnnualVestingTranches"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ecc265fc-f93b-44bb-8370-7b60a191b8ba" xlink:to="loc_cvlt_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAnnualVestingTranches_f136cd00-63ce-4753-ace1-ce81f099f1da" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/StockPlansRestrictedStockUnitsActivityDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#StockPlansRestrictedStockUnitsActivityDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/StockPlansRestrictedStockUnitsActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40c74fc7-c28f-41be-a020-50f7a67ab365" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_ab3d71bc-1dd2-4e9a-ad98-c247ca70390f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40c74fc7-c28f-41be-a020-50f7a67ab365" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_ab3d71bc-1dd2-4e9a-ad98-c247ca70390f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_25b9673f-a2c1-490d-acd4-1105d1f4b038" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_ab3d71bc-1dd2-4e9a-ad98-c247ca70390f" xlink:to="loc_us-gaap_AwardTypeAxis_25b9673f-a2c1-490d-acd4-1105d1f4b038" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_25b9673f-a2c1-490d-acd4-1105d1f4b038_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_25b9673f-a2c1-490d-acd4-1105d1f4b038" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_25b9673f-a2c1-490d-acd4-1105d1f4b038_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2d2ec04c-4328-4762-9e87-0fcfdedd8b8a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_25b9673f-a2c1-490d-acd4-1105d1f4b038" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2d2ec04c-4328-4762-9e87-0fcfdedd8b8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_996089bd-9650-4753-8465-b9235650b088" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_2d2ec04c-4328-4762-9e87-0fcfdedd8b8a" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_996089bd-9650-4753-8465-b9235650b088" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d913298d-0a6c-4429-a360-12e7b3f0c83a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40c74fc7-c28f-41be-a020-50f7a67ab365" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d913298d-0a6c-4429-a360-12e7b3f0c83a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_303c68f3-bfd6-4fdb-b94d-28daa8cdd863" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d913298d-0a6c-4429-a360-12e7b3f0c83a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_303c68f3-bfd6-4fdb-b94d-28daa8cdd863" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_7e852ae1-b8cd-4246-a2fa-2982f8dd6ba9" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d913298d-0a6c-4429-a360-12e7b3f0c83a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_7e852ae1-b8cd-4246-a2fa-2982f8dd6ba9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_0a2196a0-9f80-49aa-9b07-947a65a7d86a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d913298d-0a6c-4429-a360-12e7b3f0c83a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_0a2196a0-9f80-49aa-9b07-947a65a7d86a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_772813d5-f303-45e0-b2d4-9a68e1db4cde" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_d913298d-0a6c-4429-a360-12e7b3f0c83a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_772813d5-f303-45e0-b2d4-9a68e1db4cde" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_c42d9e8a-213f-482b-a8ae-a12ab29182b2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5bdad098-17c2-4d67-a941-2e64d18d7b97" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_40c74fc7-c28f-41be-a020-50f7a67ab365" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5bdad098-17c2-4d67-a941-2e64d18d7b97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_cdf0eb21-4242-4540-a6ad-d5bdf3cc4429" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5bdad098-17c2-4d67-a941-2e64d18d7b97" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_cdf0eb21-4242-4540-a6ad-d5bdf3cc4429" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7f3e3380-2cb5-4782-aaf1-5333db110900" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5bdad098-17c2-4d67-a941-2e64d18d7b97" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7f3e3380-2cb5-4782-aaf1-5333db110900" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_3b36f4ef-5fca-4e4e-b715-29603f422763" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5bdad098-17c2-4d67-a941-2e64d18d7b97" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_3b36f4ef-5fca-4e4e-b715-29603f422763" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_9b70f6fe-7210-4162-8da1-c008b5ab64a8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_5bdad098-17c2-4d67-a941-2e64d18d7b97" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_9b70f6fe-7210-4162-8da1-c008b5ab64a8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_57a26ca2-e4c3-4482-a0c9-31ee4d80b3ac" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/SegmentInformationScheduleofRevenuebyGeographicAreaDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#SegmentInformationScheduleofRevenuebyGeographicAreaDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/SegmentInformationScheduleofRevenuebyGeographicAreaDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_4ee8c60a-2487-42c2-8833-512196cbbcfe" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_cc7ffc13-ab47-404c-be2d-da47a43b3511" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_4ee8c60a-2487-42c2-8833-512196cbbcfe" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_cc7ffc13-ab47-404c-be2d-da47a43b3511" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_bb3115a2-a860-4458-9e92-a8a88f2514e1" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_cc7ffc13-ab47-404c-be2d-da47a43b3511" xlink:to="loc_srt_StatementGeographicalAxis_bb3115a2-a860-4458-9e92-a8a88f2514e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_bb3115a2-a860-4458-9e92-a8a88f2514e1_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_bb3115a2-a860-4458-9e92-a8a88f2514e1" xlink:to="loc_srt_SegmentGeographicalDomain_bb3115a2-a860-4458-9e92-a8a88f2514e1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_1d78d9c8-a1f6-413d-b326-54bad3e3ff99" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_bb3115a2-a860-4458-9e92-a8a88f2514e1" xlink:to="loc_srt_SegmentGeographicalDomain_1d78d9c8-a1f6-413d-b326-54bad3e3ff99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_cb9248cb-90cf-4809-874e-f3679299b09e" xlink:href="https://xbrl.sec.gov/country/2025/country-2025.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_1d78d9c8-a1f6-413d-b326-54bad3e3ff99" xlink:to="loc_country_US_cb9248cb-90cf-4809-874e-f3679299b09e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonUsMember_e5a93668-3d82-495a-bd2f-353f8989df36" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_NonUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_1d78d9c8-a1f6-413d-b326-54bad3e3ff99" xlink:to="loc_us-gaap_NonUsMember_e5a93668-3d82-495a-bd2f-353f8989df36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_0d42075d-b756-4e56-b948-1b2fe5fbf611" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_4ee8c60a-2487-42c2-8833-512196cbbcfe" xlink:to="loc_us-gaap_Revenues_0d42075d-b756-4e56-b948-1b2fe5fbf611" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/RestructuringActivityinRestructuringAccrualAdditionalInformationDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#RestructuringActivityinRestructuringAccrualAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/RestructuringActivityinRestructuringAccrualAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_68ce676d-7e1f-49d6-8386-e8316f0cc76c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_e3fa2928-32a1-4ff5-9e8e-10206cbe2974" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68ce676d-7e1f-49d6-8386-e8316f0cc76c" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_e3fa2928-32a1-4ff5-9e8e-10206cbe2974" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanAxis_8e97125c-3398-4ff7-9a99-dc3332cc2482" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringPlanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_e3fa2928-32a1-4ff5-9e8e-10206cbe2974" xlink:to="loc_us-gaap_RestructuringPlanAxis_8e97125c-3398-4ff7-9a99-dc3332cc2482" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_8e97125c-3398-4ff7-9a99-dc3332cc2482_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_8e97125c-3398-4ff7-9a99-dc3332cc2482" xlink:to="loc_us-gaap_RestructuringPlanDomain_8e97125c-3398-4ff7-9a99-dc3332cc2482_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringPlanDomain_9bde1412-3a0f-4c9c-8219-ff28c929aeab" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringPlanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_8e97125c-3398-4ff7-9a99-dc3332cc2482" xlink:to="loc_us-gaap_RestructuringPlanDomain_9bde1412-3a0f-4c9c-8219-ff28c929aeab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_A2024RestructuringProgramMember_55f83b2c-adeb-4d12-9413-2a8ad805eb86" xlink:href="cvlt-20250630.xsd#cvlt_A2024RestructuringProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringPlanDomain_9bde1412-3a0f-4c9c-8219-ff28c929aeab" xlink:to="loc_cvlt_A2024RestructuringProgramMember_55f83b2c-adeb-4d12-9413-2a8ad805eb86" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeveranceCosts1_b0e780d2-5af5-43cc-8357-2b82e65cd2c8" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SeveranceCosts1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68ce676d-7e1f-49d6-8386-e8316f0cc76c" xlink:to="loc_us-gaap_SeveranceCosts1_b0e780d2-5af5-43cc-8357-2b82e65cd2c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_2ddefdff-172e-4543-ad24-d73bd9d805f3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsForRestructuring"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68ce676d-7e1f-49d6-8386-e8316f0cc76c" xlink:to="loc_us-gaap_PaymentsForRestructuring_2ddefdff-172e-4543-ad24-d73bd9d805f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_89427540-0d08-4ebc-8b2b-137febeeadf6" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RestructuringReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_68ce676d-7e1f-49d6-8386-e8316f0cc76c" xlink:to="loc_us-gaap_RestructuringReserve_89427540-0d08-4ebc-8b2b-137febeeadf6" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/RevolvingCreditFacilityAdditionalInformationDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#RevolvingCreditFacilityAdditionalInformationDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/RevolvingCreditFacilityAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_1b1fdfad-4c03-4307-af53-a088c48ee2f7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_3dc31f93-499a-4f78-a6b8-bc800b08f38d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_1b1fdfad-4c03-4307-af53-a088c48ee2f7" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_3dc31f93-499a-4f78-a6b8-bc800b08f38d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_33d91461-83fc-4715-bf5e-f0e336ce12ee" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3dc31f93-499a-4f78-a6b8-bc800b08f38d" xlink:to="loc_us-gaap_CreditFacilityAxis_33d91461-83fc-4715-bf5e-f0e336ce12ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_33d91461-83fc-4715-bf5e-f0e336ce12ee_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_33d91461-83fc-4715-bf5e-f0e336ce12ee" xlink:to="loc_us-gaap_CreditFacilityDomain_33d91461-83fc-4715-bf5e-f0e336ce12ee_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_5ca24918-900d-4ada-a3f3-1af5f0d9523a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_33d91461-83fc-4715-bf5e-f0e336ce12ee" xlink:to="loc_us-gaap_CreditFacilityDomain_5ca24918-900d-4ada-a3f3-1af5f0d9523a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_826e7f95-40d8-4056-8436-dc25ddc19f3e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5ca24918-900d-4ada-a3f3-1af5f0d9523a" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_826e7f95-40d8-4056-8436-dc25ddc19f3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_89612801-b26a-4e72-abb1-b3cf48f56160" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3dc31f93-499a-4f78-a6b8-bc800b08f38d" xlink:to="loc_us-gaap_DebtInstrumentAxis_89612801-b26a-4e72-abb1-b3cf48f56160" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_89612801-b26a-4e72-abb1-b3cf48f56160_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_89612801-b26a-4e72-abb1-b3cf48f56160" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_89612801-b26a-4e72-abb1-b3cf48f56160_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_bc13bbc8-6499-432b-826d-883009cfd22e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_89612801-b26a-4e72-abb1-b3cf48f56160" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_bc13bbc8-6499-432b-826d-883009cfd22e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SeniorSecuredRevolvingCreditFacilityMember_e97eab66-8565-4194-b353-640949bec74a" xlink:href="cvlt-20250630.xsd#cvlt_SeniorSecuredRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_bc13bbc8-6499-432b-826d-883009cfd22e" xlink:to="loc_cvlt_SeniorSecuredRevolvingCreditFacilityMember_e97eab66-8565-4194-b353-640949bec74a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_fde12701-6778-4fbb-a524-646c289eda2c" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3dc31f93-499a-4f78-a6b8-bc800b08f38d" xlink:to="loc_srt_RangeAxis_fde12701-6778-4fbb-a524-646c289eda2c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_fde12701-6778-4fbb-a524-646c289eda2c_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_fde12701-6778-4fbb-a524-646c289eda2c" xlink:to="loc_srt_RangeMember_fde12701-6778-4fbb-a524-646c289eda2c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f4a9483d-a109-4f8f-9d55-16d8a6ed5120" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_fde12701-6778-4fbb-a524-646c289eda2c" xlink:to="loc_srt_RangeMember_f4a9483d-a109-4f8f-9d55-16d8a6ed5120" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_2501244b-a8bf-4853-8324-d805292ced0a" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f4a9483d-a109-4f8f-9d55-16d8a6ed5120" xlink:to="loc_srt_MinimumMember_2501244b-a8bf-4853-8324-d805292ced0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_1c94be96-44bb-4501-b41d-f107c634ad16" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f4a9483d-a109-4f8f-9d55-16d8a6ed5120" xlink:to="loc_srt_MaximumMember_1c94be96-44bb-4501-b41d-f107c634ad16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_32aae927-6ab1-49a4-8cd0-699ae6dc3441" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_3dc31f93-499a-4f78-a6b8-bc800b08f38d" xlink:to="loc_us-gaap_VariableRateAxis_32aae927-6ab1-49a4-8cd0-699ae6dc3441" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_32aae927-6ab1-49a4-8cd0-699ae6dc3441_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_32aae927-6ab1-49a4-8cd0-699ae6dc3441" xlink:to="loc_us-gaap_VariableRateDomain_32aae927-6ab1-49a4-8cd0-699ae6dc3441_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_023fffb9-e8d6-4db9-9576-0c7ebd30f8af" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_32aae927-6ab1-49a4-8cd0-699ae6dc3441" xlink:to="loc_us-gaap_VariableRateDomain_023fffb9-e8d6-4db9-9576-0c7ebd30f8af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_ed76d2ad-7ff2-42a5-8740-ed8e2a024247" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_023fffb9-e8d6-4db9-9576-0c7ebd30f8af" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_ed76d2ad-7ff2-42a5-8740-ed8e2a024247" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrimeRateMember_cd81f984-529b-44cb-a416-f11102a20514" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PrimeRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_023fffb9-e8d6-4db9-9576-0c7ebd30f8af" xlink:to="loc_us-gaap_PrimeRateMember_cd81f984-529b-44cb-a416-f11102a20514" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_c3fdc54f-78b9-472f-8bb8-fa3eaa1d4715" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_1b1fdfad-4c03-4307-af53-a088c48ee2f7" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_c3fdc54f-78b9-472f-8bb8-fa3eaa1d4715" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTerm_f142825e-7e18-46b8-911c-6aeaa0afe54e" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_1b1fdfad-4c03-4307-af53-a088c48ee2f7" xlink:to="loc_us-gaap_DebtInstrumentTerm_f142825e-7e18-46b8-911c-6aeaa0afe54e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_72dd44d1-500a-4e6c-81b2-abe2543d2f33" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_1b1fdfad-4c03-4307-af53-a088c48ee2f7" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_72dd44d1-500a-4e6c-81b2-abe2543d2f33" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_0391a0e0-c450-49f0-911a-11ac1b84ee3d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_1b1fdfad-4c03-4307-af53-a088c48ee2f7" xlink:to="loc_us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_0391a0e0-c450-49f0-911a-11ac1b84ee3d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_86961728-ca6d-464a-afcb-a11a35abe749" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_1b1fdfad-4c03-4307-af53-a088c48ee2f7" xlink:to="loc_us-gaap_LineOfCredit_86961728-ca6d-464a-afcb-a11a35abe749" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_544a2b8f-76bf-4878-966e-86b171e80f06" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_1b1fdfad-4c03-4307-af53-a088c48ee2f7" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_544a2b8f-76bf-4878-966e-86b171e80f06" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/RevolvingCreditFacilityAmortizationofDebtIssuanceCostsandInterestExpenseDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#RevolvingCreditFacilityAmortizationofDebtIssuanceCostsandInterestExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/RevolvingCreditFacilityAmortizationofDebtIssuanceCostsandInterestExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_0b706e79-8926-4dac-9497-98889071a739" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_f89e8769-8620-4ee4-bc19-0561fa75d3ed" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_0b706e79-8926-4dac-9497-98889071a739" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_f89e8769-8620-4ee4-bc19-0561fa75d3ed" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_9804e1d7-e229-43ca-975b-1e1aba0e6554" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_f89e8769-8620-4ee4-bc19-0561fa75d3ed" xlink:to="loc_us-gaap_CreditFacilityAxis_9804e1d7-e229-43ca-975b-1e1aba0e6554" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_9804e1d7-e229-43ca-975b-1e1aba0e6554_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_9804e1d7-e229-43ca-975b-1e1aba0e6554" xlink:to="loc_us-gaap_CreditFacilityDomain_9804e1d7-e229-43ca-975b-1e1aba0e6554_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_04d83141-7505-404b-a9e9-95593b59757f" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_9804e1d7-e229-43ca-975b-1e1aba0e6554" xlink:to="loc_us-gaap_CreditFacilityDomain_04d83141-7505-404b-a9e9-95593b59757f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_9636de8f-7726-44ae-a445-98cfe3abd8e7" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_04d83141-7505-404b-a9e9-95593b59757f" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_9636de8f-7726-44ae-a445-98cfe3abd8e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_8c1e48ee-2daf-4bf1-b5e5-cebff8255f84" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_f89e8769-8620-4ee4-bc19-0561fa75d3ed" xlink:to="loc_us-gaap_DebtInstrumentAxis_8c1e48ee-2daf-4bf1-b5e5-cebff8255f84" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_8c1e48ee-2daf-4bf1-b5e5-cebff8255f84_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_8c1e48ee-2daf-4bf1-b5e5-cebff8255f84" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_8c1e48ee-2daf-4bf1-b5e5-cebff8255f84_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_e1522b15-1323-491f-9ff1-d5bde90a9a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_8c1e48ee-2daf-4bf1-b5e5-cebff8255f84" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_e1522b15-1323-491f-9ff1-d5bde90a9a7a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SeniorSecuredRevolvingCreditFacilityMember_0574367e-73c4-4247-8190-163ad8d1d9cb" xlink:href="cvlt-20250630.xsd#cvlt_SeniorSecuredRevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_e1522b15-1323-491f-9ff1-d5bde90a9a7a" xlink:to="loc_cvlt_SeniorSecuredRevolvingCreditFacilityMember_0574367e-73c4-4247-8190-163ad8d1d9cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_39986dad-5be5-4c1b-b371-85df1f364ebc" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_0b706e79-8926-4dac-9497-98889071a739" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_39986dad-5be5-4c1b-b371-85df1f364ebc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtExcludingAmortization_9be03cb4-aae2-4eaa-8144-2a9e4cc86b2c" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebtExcludingAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_0b706e79-8926-4dac-9497-98889071a739" xlink:to="loc_us-gaap_InterestExpenseDebtExcludingAmortization_9be03cb4-aae2-4eaa-8144-2a9e4cc86b2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_225fe9e9-fc85-438d-8fc3-cbadcfa4767b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_0b706e79-8926-4dac-9497-98889071a739" xlink:to="loc_us-gaap_InterestExpenseDebt_225fe9e9-fc85-438d-8fc3-cbadcfa4767b" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.commvault.com/role/SubsequentEventDetails" xlink:type="simple" xlink:href="cvlt-20250630.xsd#SubsequentEventDetails"/>
  <link:definitionLink xlink:role="http://www.commvault.com/role/SubsequentEventDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_a4ba5c2f-64ce-4418-b7a5-a40540957eb3" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_f31568b2-2712-435a-9167-0a8cfab7ec66" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_a4ba5c2f-64ce-4418-b7a5-a40540957eb3" xlink:to="loc_us-gaap_SubsequentEventTable_f31568b2-2712-435a-9167-0a8cfab7ec66" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_11e95a45-a4a5-4a82-b8bc-c435f0a12565" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_f31568b2-2712-435a-9167-0a8cfab7ec66" xlink:to="loc_srt_StatementScenarioAxis_11e95a45-a4a5-4a82-b8bc-c435f0a12565" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_11e95a45-a4a5-4a82-b8bc-c435f0a12565_default" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_11e95a45-a4a5-4a82-b8bc-c435f0a12565" xlink:to="loc_srt_ScenarioUnspecifiedDomain_11e95a45-a4a5-4a82-b8bc-c435f0a12565_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_583c25a9-a277-4c4d-aff0-c0d5bd3f61f5" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_11e95a45-a4a5-4a82-b8bc-c435f0a12565" xlink:to="loc_srt_ScenarioUnspecifiedDomain_583c25a9-a277-4c4d-aff0-c0d5bd3f61f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioForecastMember_ed7e1261-e243-45a0-b02d-3916980872b3" xlink:href="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd#srt_ScenarioForecastMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ScenarioUnspecifiedDomain_583c25a9-a277-4c4d-aff0-c0d5bd3f61f5" xlink:to="loc_srt_ScenarioForecastMember_ed7e1261-e243-45a0-b02d-3916980872b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_a10462d2-6b4b-422c-b4cd-eacb09dda17b" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_f31568b2-2712-435a-9167-0a8cfab7ec66" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_a10462d2-6b4b-422c-b4cd-eacb09dda17b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a10462d2-6b4b-422c-b4cd-eacb09dda17b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_a10462d2-6b4b-422c-b4cd-eacb09dda17b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a10462d2-6b4b-422c-b4cd-eacb09dda17b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_21666c34-4f59-4395-927f-c0faaa16ee9d" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_a10462d2-6b4b-422c-b4cd-eacb09dda17b" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_21666c34-4f59-4395-927f-c0faaa16ee9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_SatoriCyberLtdMember_4c9916c0-490f-45be-81d0-775fe0ccf554" xlink:href="cvlt-20250630.xsd#cvlt_SatoriCyberLtdMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_21666c34-4f59-4395-927f-c0faaa16ee9d" xlink:to="loc_cvlt_SatoriCyberLtdMember_4c9916c0-490f-45be-81d0-775fe0ccf554" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_a2cd71a9-47ba-4762-a099-02a9e62b9724" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_f31568b2-2712-435a-9167-0a8cfab7ec66" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_a2cd71a9-47ba-4762-a099-02a9e62b9724" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_a2cd71a9-47ba-4762-a099-02a9e62b9724_default" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_a2cd71a9-47ba-4762-a099-02a9e62b9724" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_a2cd71a9-47ba-4762-a099-02a9e62b9724_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_e79cdebf-36fc-4c29-a883-193e220ebfc2" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_a2cd71a9-47ba-4762-a099-02a9e62b9724" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_e79cdebf-36fc-4c29-a883-193e220ebfc2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_cefa5d2e-b068-4157-a600-c9d19980edcd" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_e79cdebf-36fc-4c29-a883-193e220ebfc2" xlink:to="loc_us-gaap_SubsequentEventMember_cefa5d2e-b068-4157-a600-c9d19980edcd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_b7fabcbb-121e-4e71-a19f-a72d87536d84" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_a4ba5c2f-64ce-4418-b7a5-a40540957eb3" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_b7fabcbb-121e-4e71-a19f-a72d87536d84" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_JenniferDiRicoMember_d199a81b-e2e2-45c3-a579-6f46c25c1932" xlink:href="cvlt-20250630.xsd#cvlt_JenniferDiRicoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_cvlt_JenniferDiRicoMember_d199a81b-e2e2-45c3-a579-6f46c25c1932" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_cvlt_GaryMerrillMember_19dea411-5a01-4d82-bad7-4953099f0cca" xlink:href="cvlt-20250630.xsd#cvlt_GaryMerrillMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_cvlt_GaryMerrillMember_19dea411-5a01-4d82-bad7-4953099f0cca" xlink:type="arc" order="3"/>
  </link:definitionLink>
</link:linkbase>
