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

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:cac9ad18-38a6-4f4d-8d18-7872f6d354c2,g:4d716b6f-7923-428f-b314-54db3b3a9f25-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:it="http://www.gartner.com/20230331" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://www.gartner.com/20230331">
  <xs:import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd"/>
  <xs:import namespace="http://www.w3.org/1999/xlink" schemaLocation="http://www.xbrl.org/2003/xlink-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2022" schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="it-20230331_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="it-20230331_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="it-20230331_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="it-20230331_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="CoverPage" roleURI="http://www.gartner.com/role/CoverPage">
        <link:definition>0000001 - Document - Cover Page</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheets" roleURI="http://www.gartner.com/role/CondensedConsolidatedBalanceSheets">
        <link:definition>0000002 - Statement - Condensed Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedBalanceSheetsParentheticals" roleURI="http://www.gartner.com/role/CondensedConsolidatedBalanceSheetsParentheticals">
        <link:definition>0000003 - Statement - Condensed Consolidated Balance Sheets (Parentheticals)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofOperations" roleURI="http://www.gartner.com/role/CondensedConsolidatedStatementsofOperations">
        <link:definition>0000004 - Statement - Condensed Consolidated Statements of Operations</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofComprehensiveIncome" roleURI="http://www.gartner.com/role/CondensedConsolidatedStatementsofComprehensiveIncome">
        <link:definition>0000005 - Statement - Condensed Consolidated Statements of Comprehensive Income</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofChangesinStockholdersEquity" roleURI="http://www.gartner.com/role/CondensedConsolidatedStatementsofChangesinStockholdersEquity">
        <link:definition>0000006 - Statement - Condensed Consolidated Statements of Changes in Stockholders' Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="CondensedConsolidatedStatementsofCashFlows" roleURI="http://www.gartner.com/role/CondensedConsolidatedStatementsofCashFlows">
        <link:definition>0000007 - Statement - Condensed Consolidated Statements of Cash Flows</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessandBasisofPresentation" roleURI="http://www.gartner.com/role/BusinessandBasisofPresentation">
        <link:definition>0000008 - Disclosure - Business and Basis of Presentation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AcquisitionandDivestiture" roleURI="http://www.gartner.com/role/AcquisitionandDivestiture">
        <link:definition>0000009 - Disclosure - Acquisition and Divestiture</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssets" roleURI="http://www.gartner.com/role/GoodwillandIntangibleAssets">
        <link:definition>0000010 - Disclosure - Goodwill and Intangible Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueandRelatedMatters" roleURI="http://www.gartner.com/role/RevenueandRelatedMatters">
        <link:definition>0000011 - Disclosure - Revenue and Related Matters</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ComputationofEarningsPerShare" roleURI="http://www.gartner.com/role/ComputationofEarningsPerShare">
        <link:definition>0000012 - Disclosure - Computation of Earnings Per Share</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensation" roleURI="http://www.gartner.com/role/StockBasedCompensation">
        <link:definition>0000013 - Disclosure - Stock-Based Compensation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentInformation" roleURI="http://www.gartner.com/role/SegmentInformation">
        <link:definition>0000014 - Disclosure - Segment Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Debt" roleURI="http://www.gartner.com/role/Debt">
        <link:definition>0000015 - Disclosure - Debt</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Equity" roleURI="http://www.gartner.com/role/Equity">
        <link:definition>0000016 - Disclosure - Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxes" roleURI="http://www.gartner.com/role/IncomeTaxes">
        <link:definition>0000017 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DerivativesandHedging" roleURI="http://www.gartner.com/role/DerivativesandHedging">
        <link:definition>0000018 - Disclosure - Derivatives and Hedging</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueDisclosures" roleURI="http://www.gartner.com/role/FairValueDisclosures">
        <link:definition>0000019 - Disclosure - Fair Value Disclosures</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Contingencies" roleURI="http://www.gartner.com/role/Contingencies">
        <link:definition>0000020 - Disclosure - Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Leases" roleURI="http://www.gartner.com/role/Leases">
        <link:definition>0000021 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessandBasisofPresentationPolicies" roleURI="http://www.gartner.com/role/BusinessandBasisofPresentationPolicies">
        <link:definition>0000022 - Disclosure - Business and Basis of Presentation (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessandBasisofPresentationTables" roleURI="http://www.gartner.com/role/BusinessandBasisofPresentationTables">
        <link:definition>0000023 - Disclosure - Business and Basis of Presentation (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsTables" roleURI="http://www.gartner.com/role/GoodwillandIntangibleAssetsTables">
        <link:definition>0000024 - Disclosure - Goodwill and Intangible Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueandRelatedMattersTables" roleURI="http://www.gartner.com/role/RevenueandRelatedMattersTables">
        <link:definition>0000025 - Disclosure - Revenue and Related Matters (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ComputationofEarningsPerShareTables" roleURI="http://www.gartner.com/role/ComputationofEarningsPerShareTables">
        <link:definition>0000026 - Disclosure - Computation of Earnings Per Share (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationTables" roleURI="http://www.gartner.com/role/StockBasedCompensationTables">
        <link:definition>0000027 - Disclosure - Stock-Based Compensation (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentInformationTables" roleURI="http://www.gartner.com/role/SegmentInformationTables">
        <link:definition>0000028 - Disclosure - Segment Information (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtTables" roleURI="http://www.gartner.com/role/DebtTables">
        <link:definition>0000029 - Disclosure - Debt (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquityTables" roleURI="http://www.gartner.com/role/EquityTables">
        <link:definition>0000030 - Disclosure - Equity (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DerivativesandHedgingTables" roleURI="http://www.gartner.com/role/DerivativesandHedgingTables">
        <link:definition>0000031 - Disclosure - Derivatives and Hedging (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueDisclosuresTables" roleURI="http://www.gartner.com/role/FairValueDisclosuresTables">
        <link:definition>0000032 - Disclosure - Fair Value Disclosures (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesTables" roleURI="http://www.gartner.com/role/LeasesTables">
        <link:definition>0000033 - Disclosure - Leases (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessandBasisofPresentationNarrativeDetails" roleURI="http://www.gartner.com/role/BusinessandBasisofPresentationNarrativeDetails">
        <link:definition>0000034 - Disclosure - Business and Basis of Presentation - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="BusinessandBasisofPresentationCashandCashEquivalentsandRestrictedCashDetails" roleURI="http://www.gartner.com/role/BusinessandBasisofPresentationCashandCashEquivalentsandRestrictedCashDetails">
        <link:definition>0000035 - Disclosure - Business and Basis of Presentation - Cash and Cash Equivalents and Restricted Cash (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AcquisitionandDivestitureDetails" roleURI="http://www.gartner.com/role/AcquisitionandDivestitureDetails">
        <link:definition>0000036 - Disclosure - Acquisition and Divestiture (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsChangestotheCarryingAmountofGoodwillbySegmentDetails" roleURI="http://www.gartner.com/role/GoodwillandIntangibleAssetsChangestotheCarryingAmountofGoodwillbySegmentDetails">
        <link:definition>0000037 - Disclosure - Goodwill and Intangible Assets - Changes to the Carrying Amount of Goodwill by Segment (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsCarryingAmountsofAmortizableIntangibleAssetsDetails" roleURI="http://www.gartner.com/role/GoodwillandIntangibleAssetsCarryingAmountsofAmortizableIntangibleAssetsDetails">
        <link:definition>0000038 - Disclosure - Goodwill and Intangible Assets - Carrying Amounts of Amortizable Intangible Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="GoodwillandIntangibleAssetsEstimatedFutureAmortizationExpenseByYearFromAmortizableIntangiblesDetails" roleURI="http://www.gartner.com/role/GoodwillandIntangibleAssetsEstimatedFutureAmortizationExpenseByYearFromAmortizableIntangiblesDetails">
        <link:definition>0000039 - Disclosure - Goodwill and Intangible Assets - Estimated Future Amortization Expense By Year From Amortizable Intangibles (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueandRelatedMattersDisaggregationofRevenuebyGeographicAreaDetails" roleURI="http://www.gartner.com/role/RevenueandRelatedMattersDisaggregationofRevenuebyGeographicAreaDetails">
        <link:definition>0000040 - Disclosure - Revenue and Related Matters - Disaggregation of Revenue by Geographic Area (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueandRelatedMattersTimingOfRevenueRecognitionLiabilitiesperSegmentDetails" roleURI="http://www.gartner.com/role/RevenueandRelatedMattersTimingOfRevenueRecognitionLiabilitiesperSegmentDetails">
        <link:definition>0000041 - Disclosure - Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueandRelatedMattersRevenueRemainingPerformanceObligationDetails" roleURI="http://www.gartner.com/role/RevenueandRelatedMattersRevenueRemainingPerformanceObligationDetails">
        <link:definition>0000042 - Disclosure - Revenue and Related Matters - Revenue Remaining Performance Obligation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueandRelatedMattersRevenueRemainingPerformanceObligationDetails_1" roleURI="http://www.gartner.com/role/RevenueandRelatedMattersRevenueRemainingPerformanceObligationDetails_1">
        <link:definition>0000042 - Disclosure - Revenue and Related Matters - Revenue Remaining Performance Obligation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="RevenueandRelatedMattersScheduleofContractwithCustomerAssetandLiabilityDetails" roleURI="http://www.gartner.com/role/RevenueandRelatedMattersScheduleofContractwithCustomerAssetandLiabilityDetails">
        <link:definition>0000043 - Disclosure - Revenue and Related Matters - Schedule of Contract with Customer, Asset and Liability (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ComputationofEarningsPerShareCalculationsOfBasicAndDilutedLossEarningsPerShareDetails" roleURI="http://www.gartner.com/role/ComputationofEarningsPerShareCalculationsOfBasicAndDilutedLossEarningsPerShareDetails">
        <link:definition>0000044 - Disclosure - Computation of Earnings Per Share - Calculations Of Basic And Diluted (Loss) Earnings Per Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="ComputationofEarningsPerShareAdditionalinformationDetails" roleURI="http://www.gartner.com/role/ComputationofEarningsPerShareAdditionalinformationDetails">
        <link:definition>0000045 - Disclosure - Computation of Earnings Per Share - Additional information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationNarrativeDetails" roleURI="http://www.gartner.com/role/StockBasedCompensationNarrativeDetails">
        <link:definition>0000046 - Disclosure - Stock-Based Compensation - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="StockBasedCompensationStockbasedCompensationExpensebyAwardTypeandExpenseCategoryDetails" roleURI="http://www.gartner.com/role/StockBasedCompensationStockbasedCompensationExpensebyAwardTypeandExpenseCategoryDetails">
        <link:definition>0000047 - Disclosure - Stock-Based Compensation - Stock-based Compensation Expense by Award Type and Expense Category (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentInformationInformationAboutReportableSegmentsDetails" roleURI="http://www.gartner.com/role/SegmentInformationInformationAboutReportableSegmentsDetails">
        <link:definition>0000048 - Disclosure - Segment Information - Information About Reportable Segments (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SegmentInformationReconciliationofSegmentGrossContributiontoNetIncomeDetails" roleURI="http://www.gartner.com/role/SegmentInformationReconciliationofSegmentGrossContributiontoNetIncomeDetails">
        <link:definition>0000049 - Disclosure - Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtBorrowingsDetails" roleURI="http://www.gartner.com/role/DebtBorrowingsDetails">
        <link:definition>0000050 - Disclosure - Debt - Borrowings (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtFootnotetoBorrowingsDetails" roleURI="http://www.gartner.com/role/DebtFootnotetoBorrowingsDetails">
        <link:definition>0000051 - Disclosure - Debt - Footnote to Borrowings (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtNarrativeDetails" roleURI="http://www.gartner.com/role/DebtNarrativeDetails">
        <link:definition>0000052 - Disclosure - Debt - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DebtInterestRateSwapsDetails" roleURI="http://www.gartner.com/role/DebtInterestRateSwapsDetails">
        <link:definition>0000053 - Disclosure - Debt - Interest Rate Swaps (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquityShareRepurchaseProgramandShareRepurchaseActivityDetails" roleURI="http://www.gartner.com/role/EquityShareRepurchaseProgramandShareRepurchaseActivityDetails">
        <link:definition>0000054 - Disclosure - Equity - Share Repurchase Program and Share Repurchase Activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="EquityChangesinAOCILbyComponentDetails" roleURI="http://www.gartner.com/role/EquityChangesinAOCILbyComponentDetails">
        <link:definition>0000055 - Disclosure - Equity - Changes in AOCI/L by Component (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="IncomeTaxesDetails" roleURI="http://www.gartner.com/role/IncomeTaxesDetails">
        <link:definition>0000056 - Disclosure - Income Taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DerivativesandHedgingOutstandingDerivativesContractsDetails" roleURI="http://www.gartner.com/role/DerivativesandHedgingOutstandingDerivativesContractsDetails">
        <link:definition>0000057 - Disclosure - Derivatives and Hedging - Outstanding Derivatives Contracts (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="DerivativesandHedgingDerivativeGainsAndLossesThatHaveBeenRecognizedInCondensedConsolidatedStatementsOfOperationsDetails" roleURI="http://www.gartner.com/role/DerivativesandHedgingDerivativeGainsAndLossesThatHaveBeenRecognizedInCondensedConsolidatedStatementsOfOperationsDetails">
        <link:definition>0000058 - Disclosure - Derivatives and Hedging - Derivative Gains And Losses That Have Been Recognized In Condensed Consolidated Statements Of Operations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueDisclosuresAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" roleURI="http://www.gartner.com/role/FairValueDisclosuresAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails">
        <link:definition>0000059 - Disclosure - Fair Value Disclosures - Assets And Liabilities Measured At Fair Value On Recurring Basis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueDisclosuresFairValueofDebtInstrumentsDetails" roleURI="http://www.gartner.com/role/FairValueDisclosuresFairValueofDebtInstrumentsDetails">
        <link:definition>0000060 - Disclosure - Fair Value Disclosures - Fair Value of Debt Instruments (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="FairValueDisclosuresNarrativeDetails" roleURI="http://www.gartner.com/role/FairValueDisclosuresNarrativeDetails">
        <link:definition>0000061 - Disclosure - Fair Value Disclosures - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesNarrativeDetails" roleURI="http://www.gartner.com/role/LeasesNarrativeDetails">
        <link:definition>0000062 - Disclosure - Leases - Narrative (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesNetLeaseCostsDetails" roleURI="http://www.gartner.com/role/LeasesNetLeaseCostsDetails">
        <link:definition>0000063 - Disclosure - Leases - Net Lease Costs (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="LeasesSupplementalBalanceSheetInformationDetails" roleURI="http://www.gartner.com/role/LeasesSupplementalBalanceSheetInformationDetails">
        <link:definition>0000064 - Disclosure - Leases - Supplemental Balance Sheet Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="it_FloatingEurodollarBaseRate" abstract="false" name="FloatingEurodollarBaseRate" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="it_LesseeOperatingLeaseOptiontoTerminateTerm" abstract="false" name="LesseeOperatingLeaseOptiontoTerminateTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="it_PlanLiabilitiesMember" abstract="true" name="PlanLiabilitiesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_RetirementEligibleEmployeesEquityAwardMember" abstract="true" name="RetirementEligibleEmployeesEquityAwardMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_OtherInternationalMember" abstract="true" name="OtherInternationalMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_RightOfUseAssetsMember" abstract="true" name="RightOfUseAssetsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_ConnecticutEconomicDevelopmentProgramMember" abstract="true" name="ConnecticutEconomicDevelopmentProgramMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_DebtInstrumentIssuePricePercentage" abstract="false" name="DebtInstrumentIssuePricePercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="it_AccruedLiabilitiesCurrentMember" abstract="true" name="AccruedLiabilitiesCurrentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_EconomicDevelopmentLoan2Member" abstract="true" name="EconomicDevelopmentLoan2Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_PlanAssetsMember" abstract="true" name="PlanAssetsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_A2020CreditAgreementMember" abstract="true" name="A2020CreditAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_OpenMarketPurchasesMember" abstract="true" name="OpenMarketPurchasesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_ChicagoIllinoisMember" abstract="true" name="ChicagoIllinoisMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_NumeratorAbstract" abstract="true" name="NumeratorAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="it_BusinessCombinationAcquisitionandIntegrationRelatedCosts" abstract="false" name="BusinessCombinationAcquisitionandIntegrationRelatedCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="it_FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour" abstract="false" name="FiniteLivedIntangibleAssetExpectedAmortizationAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="it_IncreaseDecreaseInOperatingCapitalNetOfAcquisitionAbstract" abstract="true" name="IncreaseDecreaseInOperatingCapitalNetOfAcquisitionAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="it_OtherLongTermDebtMember" abstract="true" name="OtherLongTermDebtMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_OpenMarketPurchasesExcludedMember" abstract="true" name="OpenMarketPurchasesExcludedMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_AssetsAndLiabilitiesLeasesTableTextBlock" abstract="false" name="AssetsAndLiabilitiesLeasesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="it_SegmentReportingInformationPercentofTargetBonusChargesAllocatedtoSegments" abstract="false" name="SegmentReportingInformationPercentofTargetBonusChargesAllocatedtoSegments" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="it_VariableRateComponentsAxis" abstract="true" name="VariableRateComponentsAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="it_NetIncomePerShareBasicAndDilutedAbstract" abstract="true" name="NetIncomePerShareBasicAndDilutedAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="it_TalentNeuronMember" abstract="true" name="TalentNeuronMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_UnitedStatesAndCanadaMember" abstract="true" name="UnitedStatesAndCanadaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_StockRepurchaseProgramAdditionalAuthorizedAmount" abstract="false" name="StockRepurchaseProgramAdditionalAuthorizedAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="it_FederalReserveBoardOfNewYorkRateMember" abstract="true" name="FederalReserveBoardOfNewYorkRateMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_OperatingLeaseCostSubleasingActivities" abstract="false" name="OperatingLeaseCostSubleasingActivities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="it_VariableRateComponentsDomain" abstract="true" name="VariableRateComponentsDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_InterestExpenseandOtherNonoperatingIncome" abstract="false" name="InterestExpenseandOtherNonoperatingIncome" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="it_SeniorNotesDue2029Member" abstract="true" name="SeniorNotesDue2029Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_DebtInstrumentAdditionalInterestaboveBaseRate" abstract="false" name="DebtInstrumentAdditionalInterestaboveBaseRate" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="it_ConferencesMember" abstract="true" name="ConferencesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_DenominatorAbstract" abstract="true" name="DenominatorAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="it_ResearchRevenueMember" abstract="true" name="ResearchRevenueMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_EventsMember" abstract="true" name="EventsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_DebtInstrumentRedemptionOptionAxis" abstract="true" name="DebtInstrumentRedemptionOptionAxis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType"/>
  <xs:element id="it_EuropeMiddleEastAfricaMember" abstract="true" name="EuropeMiddleEastAfricaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_DebtInstrumentRedemptionOptionOneMember" abstract="true" name="DebtInstrumentRedemptionOptionOneMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_SeniorNotesDue2028Member" abstract="true" name="SeniorNotesDue2028Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_TermLoanFacilityMember" abstract="true" name="TermLoanFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_TreasuryStockAveragePricePaidPerShare" abstract="false" name="TreasuryStockAveragePricePaidPerShare" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="it_OperatingLeaseRightOfUseAssetReductionInCarryingAmount" abstract="false" name="OperatingLeaseRightOfUseAssetReductionInCarryingAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="it_CommonStockEquivalentsMember" abstract="true" name="CommonStockEquivalentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_DebtInstrumentRedemptionOptionDomain" abstract="true" name="DebtInstrumentRedemptionOptionDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_ResearchSegmentMember" abstract="true" name="ResearchSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_CorporateAndReconcilingItemsMember" abstract="true" name="CorporateAndReconcilingItemsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_ConsultingMember" abstract="true" name="ConsultingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_VariableRateComponentOneMember" abstract="true" name="VariableRateComponentOneMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_SeniorNotesDue2030Member" abstract="true" name="SeniorNotesDue2030Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="it_UnrecognizedTaxBenefitsReductionsResultingFromSettlementsWithTaxingAuthoritiesAndLapseOfApplicableStatuteOfLimitations" abstract="false" name="UnrecognizedTaxBenefitsReductionsResultingFromSettlementsWithTaxingAuthoritiesAndLapseOfApplicableStatuteOfLimitations" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
