<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-06-05</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000749251</issuerCik>
        <issuerName>GARTNER INC</issuerName>
        <issuerTradingSymbol>IT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001159187</rptOwnerCik>
            <rptOwnerName>UBBEN JEFFREY W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE, FOURTH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001129787</rptOwnerCik>
            <rptOwnerName>VA PARTNERS LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>FOURTH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001375350</rptOwnerCik>
            <rptOwnerName>VA Partners III, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE, 4TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001351069</rptOwnerCik>
            <rptOwnerName>ValueAct Capital Management, L.P.</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE, 4TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001351073</rptOwnerCik>
            <rptOwnerName>ValueAct Capital Management, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>435 PACIFIC AVENUE, 4TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SAN FRANCISCO</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94133</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000937541</rptOwnerCik>
            <rptOwnerName>KAMIN PETER H</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>265 FRANKLIN STREET, 16TH FLOOR</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02110</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-06-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4791</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4791</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-06-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4791</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2007-06-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F3"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4791</value>
                    <footnoteId id="F3"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18636437</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F4"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2000000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F5"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-06-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4791</value>
                    <footnoteId id="F1"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F7"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2007-06-05</value>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2007-06-05</value>
                <footnoteId id="F6"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4791</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-06-05</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2576</value>
                    <footnoteId id="F8"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F7"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2008-06-05</value>
            </exerciseDate>
            <expirationDate>
                <value>2008-06-05</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2756</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2576</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Represents Restricted Stock Units that released.</footnote>
        <footnote id="F2">Under an agreement with ValueAct Capital, Jeffrey W. Ubben is deemed to hold the common stock and restricted stock units for the benefit of ValueAct Capital Master Fund, L.P. and indirectly for  (i) VA Partners, L.L.C. as General Partner of ValueAct Capital Master Fund, L.P., (ii) ValueAct Capital Management, L.P. as the manager of ValueAct Capital Master Fund, L.P. and (iii) ValueAct Capital Management, LLC as General Partner of ValueAct Capital Management, L.P.  Jeffrey W. Ubben is a director of Gartner, Inc. and Managing Member of VA Partners, LLC and ValueAct Capital Management, LLC.  Peter H. Kamin and George F. Hamel, Jr. are Managing Members of VA Partners, LLC and ValueAct Capital Management, LLC. The reporting persons disclaim beneficial ownership of the reported stock except to the extent of their pecuniary interest therein.</footnote>
        <footnote id="F3">Jeffrey W. Ubben transferred direct ownership of the reported stock to ValueAct Capital Master Fund, L.P. in a transaction not involving any consideration in accordance with his agreement with ValueAct Capital described in (2) above.</footnote>
        <footnote id="F4">The reported stock is owned directly by ValueAct Capital Master Fund, L.P and may be deemed to be beneficially owned by (i) VA Partners, L.L.C. as General Partner of ValueAct Capital Master Fund, L.P., (ii) ValueAct Capital Management, L.P. as the manager of ValueAct Capital Master Fund, L.P. and (iii) ValueAct Capital Management, LLC as General Partner of ValueAct Capital Management, L.P.  Jeffrey W. Ubben, Peter H. Kamin and George F. Hamel, Jr. are Managing Members of VA Partners, L.L.C. and ValueAct Capital Management, LLC. The reporting person disclaims beneficial ownership of the reported stock except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F5">The reported stock is owned directly by ValueAct Capital Master Fund III, L.P and may be deemed to be beneficially owned by (i) VA Partners III, L.L.C. as General Partner of ValueAct Capital Master Fund III, L.P., (ii) ValueAct Capital Management, L.P. as the manager of ValueAct Capital Master Fund III, L.P. and (iii) ValueAct Capital Management, LLC as General Partner of ValueAct Capital Management, L.P.  Jeffrey W. Ubben, Peter H. Kamin and George F.  Hamel, Jr. are Managing Members of VA Partners III, L.L.C. and ValueAct Capital Management, LLC. The reporting person disclaims beneficial ownership of the reported stock except to the extent of his pecuniary interest therein.</footnote>
        <footnote id="F6">One Hundred Percent (100%) of the Restricted Stock Units shall vest on the date of the 2007 annual meeting of stockholders, subject to Grantee's Continued Service through such date.</footnote>
        <footnote id="F7">Column 8 is not a required reportable field.</footnote>
        <footnote id="F8">One Hundred Percent (100%) of the Restricted Stock Units shall vest on the date of the 2008 annual meeting of stockholders subject to Grantee's Continued Service through such date.  The date of the 2008 annual meeting of stockholders is not confirmed as of now.</footnote>
    </footnotes>

    <remarks>Joint Filer Information:

Name: ValueAct Capital Master Fund, L.P.,
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: Jeffrey W. Ubben
Issuer and Ticker Symbol: Gartner, Inc. (IT)
Date of Event Requiring Statement: June 5, 2007

Name: VA Partners, LLC
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: Jeffrey W. Ubben
Issuer and Ticker Symbol: Gartner, Inc. (IT)
Date of Event Requiring Statement: June 5, 2007

Name: ValueAct Capital Master Fund III, L.P.,
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: Jeffrey W. Ubben
Issuer and Ticker Symbol: Gartner, Inc. (IT)
Date of Event Requiring Statement: June 5, 2007

Name: VA Partners III, LLC
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: Jeffrey W. Ubben
Issuer and Ticker Symbol: Gartner, Inc. (IT)
Date of Event Requiring Statement: June 5, 2007

Name: ValueAct Capital Management, L.P.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: Jeffrey W. Ubben
Issuer and Ticker Symbol: Gartner, Inc. (IT)
Date of Event Requiring Statement: June 5, 2007

Name: ValueAct Capital Management, LLC
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: Jeffrey W. Ubben
Issuer and Ticker Symbol: Gartner, Inc. (IT)
Date of Event Requiring Statement: June 5, 2007

Name: George F. Hamel, Jr.
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: Jeffrey W. Ubben
Issuer and Ticker Symbol: Gartner, Inc. (IT)
Date of Event Requiring Statement: June 5, 2007

Name: Peter H. Kamin
Address: 435 Pacific Avenue, Fourth Floor, San Francisco, CA 94133
Designated Filer: Jeffrey W. Ubben
Issuer and Ticker Symbol: Gartner, Inc. (IT)
Date of Event Requiring Statement: June 5, 2007</remarks>

    <ownerSignature>
        <signatureName>/s/ Jeffrey W. Ubben</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>VA Partners, LLC, By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>ValueAct Capital Master Fund, LP, By: VA Partners, LLC, its General Partner, By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>VA Partners III, LLC, By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>ValueAct Capital Master Fund III, LP, By: VA Partners III, LLC, its General Partner, By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>ValueAct Capital Management, LP, By: ValueAct Capital Management, LLC, By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>ValueAct Capital Management, LLC, By: /s/ George F. Hamel, Jr., Managing Member</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ George F. Hamel, Jr.</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>

    <ownerSignature>
        <signatureName>/s/ Peter H. Kamin</signatureName>
        <signatureDate>2007-06-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
