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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-12-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000849636</issuerCik>
        <issuerName>RespireRx Pharmaceuticals Inc.</issuerName>
        <issuerTradingSymbol>RSPI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001363763</rptOwnerCik>
            <rptOwnerName>Lippa Arnold</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O RESPIRERX PHARMACEUTICALS INC.</rptOwnerStreet1>
            <rptOwnerStreet2>126 VALLEY ROAD, SUITE C</rptOwnerStreet2>
            <rptOwnerCity>GLEN ROCK</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07452</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Exec Chairman, CSO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.45</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-12-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>559595</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-12-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Commn Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>559595</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>559595</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.45</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-12-09</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>G</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F2"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>559595</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-12-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Commmon Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>559595</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On December 9, 2017, Dr. Lippa forgave all of the accrued but unpaid compensation to which, pursuant to his employment agreement, he was entitled as of September 30, 2017, an aggregate of $807,497.  On that date, the Company granted to Dr. Lippa options to purchase 559,595 shares of the Company's common stock, with a black-scholes value of $1.44 per option and an aggregate value of $807,497.  These Common Stock Options vested upon issuance.</footnote>
        <footnote id="F2">Dr. Lippa gifted these Common Stock Options into a family trust for estate planning purposes. He is not the trustee and does not exercise voting or investment control over shares held in the trust but he is a beneficiary of the trust.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Arnold Lippa</signatureName>
        <signatureDate>2017-12-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
