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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-10-23</periodOfReport>

    <issuer>
        <issuerCik>0001288776</issuerCik>
        <issuerName>Google Inc.</issuerName>
        <issuerTradingSymbol>GOOG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001244892</rptOwnerCik>
            <rptOwnerName>MATHER ANN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O GOOGLE INC.</rptOwnerStreet1>
            <rptOwnerStreet2>1600 AMPHITHEATRE PARKWAY</rptOwnerStreet2>
            <rptOwnerCity>MOUNTAIN VIEW</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>94043</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Google Stock Unit</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <transactionDate>
                <value>2009-10-23</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>235</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>554.0475</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2870</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Option To Purchase Class A Common Stock</value>
                <footnoteId id="F3"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>414.09</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-12-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2015-12-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Class A Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>12000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The Google Stock Units (&quot;GSUs&quot;) entitle the reporting person to receive one share of Google Inc.'s Class A common stock for each share underlying the GSU as the GSU vests. The GSUs vest as follows: (i) 1/5 th on the one year anniversary of the vesting commencement date (which was November 9, 2005) and (ii) 1/20th each quarter thereafter, subject to continued service to Google Inc. on the applicable vesting date.   The GSU is subject to the terms and conditions of Google Inc.'s 2004 Stock Plan.</footnote>
        <footnote id="F2">Class A Common Stock were sold on the transaction date, reflecting the vesting of GSUs, and the accompanying entitlement to receive one share of Google Inc.'s Class A common stock for each GSU.</footnote>
        <footnote id="F3">Shares subject to this option began vesting on November 9, 2005 and vest as follows:(i) 1/5th on the one year anniversary of the vesting commencement date and (ii) 1/60th each month thereafter, subject to continued service to Google Inc. on the applicable vesting date. The stock is subject to the terms and conditions of Google Inc.'s 2004 Stock Plan.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Jonathan Frankel as attorney-in-fact for Ann Mather</signatureName>
        <signatureDate>2009-10-26</signatureDate>
    </ownerSignature>
</ownershipDocument>
