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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2017-09-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001236365</rptOwnerCik>
            <rptOwnerName>MANUSO JAMES S J</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>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
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            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2017-09-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1097</value>
                    <footnoteId id="F5"/>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
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                    <value>74252</value>
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                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
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            <transactionDate>
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                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness>
                <value></value>
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                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
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                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2015-09-15</value>
            </exerciseDate>
            <expirationDate>
                <value>2020-09-30</value>
            </expirationDate>
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                    <value>Common Stock</value>
                </underlyingSecurityTitle>
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                </directOrIndirectOwnership>
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            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
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            <conversionOrExercisePrice>
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            </conversionOrExercisePrice>
            <transactionDate>
                <value>2017-12-09</value>
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                <transactionFormType>4</transactionFormType>
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            <transactionTimeliness>
                <value></value>
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                <transactionPricePerShare>
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            <expirationDate>
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            </expirationDate>
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            <expirationDate>
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                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
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            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
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            <exerciseDate>
                <footnoteId id="F4"/>
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            <expirationDate>
                <value>2022-01-17</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Commmon Stock</value>
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                <underlyingSecurityShares>
                    <value>75000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>75000</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>COmmon Stock Warrants (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.83</value>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2016-04-07</value>
            </exerciseDate>
            <expirationDate>
                <value>2020-09-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>36578</value>
                    <footnoteId id="F5"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                    <footnoteId id="F5"/>
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                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Common Stock Warrants (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.5</value>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2016-02-04</value>
            </exerciseDate>
            <expirationDate>
                <value>2019-02-04</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
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                    <footnoteId id="F5"/>
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            </underlyingSecurity>
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                    <footnoteId id="F5"/>
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                <directOrIndirectOwnership>
                    <value>D</value>
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        <derivativeHolding>
            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
            </securityTitle>
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                <footnoteId id="F5"/>
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            <exerciseDate>
                <footnoteId id="F6"/>
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            <expirationDate>
                <value>2021-03-31</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
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                <underlyingSecurityShares>
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                    <footnoteId id="F5"/>
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                    <footnoteId id="F5"/>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.396</value>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F7"/>
            </exerciseDate>
            <expirationDate>
                <value>2025-08-18</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>15634</value>
                    <footnoteId id="F5"/>
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                <sharesOwnedFollowingTransaction>
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                    <footnoteId id="F5"/>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.396</value>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F7"/>
            </exerciseDate>
            <expirationDate>
                <value>2025-08-18</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
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                <underlyingSecurityShares>
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                    <footnoteId id="F5"/>
                </sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
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        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Dr. Manuso purchased shares and warrants in a private transaction for an aggregate of $5,000, or $4.56 per unit, with each unit consisting of one share and warrants to purchase two additional shares of the Company's common stock.</footnote>
        <footnote id="F2">On December 9, 2017, Dr. Manuso 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 $878,360.  On that date, the Company granted to Dr. Manuso options to purchase 608,704 shares of the Company's common stock, with a black-scholes value of $1.44 per option and an aggregate value of $878,360.  These Common Stock Options vested upon issuance.</footnote>
        <footnote id="F3">These Common Stock Options vested upon issuance.</footnote>
        <footnote id="F4">These Common Stock Options vested in three installments:  25 percent on January 18, 2017 (the grant date), 25 percent on March 31, 2017, and 50 percent on June 30, 2017, and are all currently vested.</footnote>
        <footnote id="F5">The exercise price and number of shares of these securities have been adjusted to reflect the Company's 325-to-1 reverse stock split effective September 1, 2016.</footnote>
        <footnote id="F6">These Common Stock Options vested in four equal installments:  25 percent on March 31, 2016 (the grant date), 25 percent on June 30, 2016, 25 percent on September 30, 2016, and 25 percent on December 31, 2016, and are all currently vested.</footnote>
        <footnote id="F7">These Common Stock Options vested in three installments:  50 percent on August 18, 2015 (the grant date), 25 percent on February 18, 2016, and 25 percent on August 18, 2016, and are all currently vested.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ James S. Manuso</signatureName>
        <signatureDate>2017-12-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
