<?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>0001559509</rptOwnerCik>
            <rptOwnerName>SAPIRSTEIN JAMES</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>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </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>38114</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>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>38114</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>38114</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
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            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
            </securityTitle>
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            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-06-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
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                </sharesOwnedFollowingTransaction>
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                    <value>D</value>
                </directOrIndirectOwnership>
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        <derivativeHolding>
            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>3.9</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-01-18</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
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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>
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                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <value>2021-03-31</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>30770</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30770</value>
                    <footnoteId id="F4"/>
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        <derivativeHolding>
            <securityTitle>
                <value>Common Stock Options (to purchase shares of Common Stock)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.396</value>
                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-08-18</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>9231</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
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                    <footnoteId id="F4"/>
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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>8.125</value>
                <footnoteId id="F4"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F7"/>
            </exerciseDate>
            <expirationDate>
                <value>2022-06-30</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>6154</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>6154</value>
                    <footnoteId id="F4"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On December 9, 2017, Mr. Sapirstein forgave all of the accrued but unpaid directors fees to which he was entitled as of September 30, 2017, an aggregate of $55,000.  On that date, the Company granted to Mr. Sapirstein options to purchase 38,114 shares of the Company's common stock, with a black-scholes value of $1.44 per option and an aggregate value of $55,000.  These Common Stock Options vested upon issuance.</footnote>
        <footnote id="F2">These Common Stock Options vested upon issuance.</footnote>
        <footnote id="F3">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="F4">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, and are all currently vested.</footnote>
        <footnote id="F5">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="F6">These Common Stock Options vested in four equal installments:  25 percent on December 31, 2015, 25 percent on March 31, 2016, 25 percent on June 30, 2016, and 25 percent on September 30, 2016, and are all currently vested.</footnote>
        <footnote id="F7">The Common Stock Options vested in three installments:  50 percent on June 30, 2015, 25 percent on September 30, 2015, and 25 percent on December 31, 2015, and are all currently vested.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ James E. Sapirstein</signatureName>
        <signatureDate>2017-12-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
