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

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2024-05-03</periodOfReport>

    <issuer>
        <issuerCik>0000034088</issuerCik>
        <issuerName>EXXON MOBIL CORP</issuerName>
        <issuerTradingSymbol>XOM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001123847</rptOwnerCik>
            <rptOwnerName>HOOLEY JOSEPH L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O EXXON MOBIL CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>22777 SPRINGWOODS VILLAGE PKWY</rptOwnerStreet2>
            <rptOwnerCity>SPRING</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>77389</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2024-05-03</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>218</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>218</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Revocable trust with spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Shares of XOM common stock received by the reporting person automatically on May 3, 2024, pursuant to the Agreement and Plan of Merger, dated as of October 10, 2023, by and among Pioneer Natural Resources Company (&quot;Pioneer&quot;), XOM and SPQR, LLC, a wholly owned subsidiary of XOM, pursuant to which each share of Pioneer stock was converted into the right to receive 2.3234 shares of XOM common stock.</footnote>
        <footnote id="F2">Reporting person is co-trustee with spouse in revocable trust.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Angela M. Sage by Power of Attorney</signatureName>
        <signatureDate>2024-08-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
