Exhibit 24

                               POWER OF ATTORNEY

     Know all by these presents, that the undersigned hereby constitutes and
appoints each of the Chief Executive Officer, who is currently Terrie Curran,
the Chief Financial Officer, who is currently Molly Henderson, and the General
Counsel and Corporate Secretary, who is currently Larry Miller, and their
respective successors, signing singly, the undersigned's true and lawful
attorney-in-fact to:

     (1)   prepare, execute in the undersigned's name and on the undersigned's
     behalf, and submit to the U.S. Securities and Exchange Commission (the
     "SEC") a Form ID, including amendments thereto, and any other documents
     necessary or appropriate to obtain codes and passwords enabling the
     undersigned to make electronic filings with the SEC of reports required by
     Section 16(a) of the Securities Exchange Act of 1934 or any rule or
     regulation of the SEC;

     (2)   execute for and on behalf of the undersigned, in the undersigned's
     capacity as an officer and/or director of Phathom Pharmaceuticals, Inc., a
     Delaware corporation (the "Company") and/or beneficial owner of more than
     10% of the Company's capital stock, Forms 3, 4, and 5 and any amendments
     thereto in accordance with Section 16(a) of the Securities Exchange Act of
     1934 and the rules thereunder;

     (3)   do and perform any and all acts for and on behalf of the undersigned
     which may be necessary or desirable to complete and execute any such Form
     3, 4, or 5, complete and execute any amendment or amendments thereto, and
     timely file such form with the SEC and any stock exchange or similar
     authority; and

     (4)   take any other action of any type whatsoever in connection with the
     foregoing which, in the opinion of such attorney-in-fact, may be of
     benefit to, in the best interest of, or legally required by, the
     undersigned, it being understood that the documents executed by such
     attorney-in-fact on behalf of the undersigned pursuant to this Power of
     Attorney shall be in such form and shall contain such terms and conditions
     as such attorney-in-fact may approve in such attorney-in-fact's discretion.

     The undersigned hereby grants to each such attorney-in-fact full power and
authority to do and perform any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned
might or could do if personally present, with full power of substitution or
revocation, hereby ratifying and confirming all that such attorney-in-fact, or
such attorney-in-fact's substitute or substitutes, shall lawfully do or cause to
be done by virtue of this Power of Attorney and the rights and powers herein
granted. The undersigned acknowledges that the foregoing attorneys-in-fact, in
serving in such capacity at the request of the undersigned, are not assuming,
nor is the Company assuming, any of the undersigned's responsibilities to comply
with Section 16 of the Securities Exchange Act of 1934.

     The undersigned agrees that each such attorney-in-fact herein may rely
entirely on information furnished orally or in writing by the undersigned to
such attorney-in-fact. The undersigned also agrees to indemnify and hold
harmless the Company and each such attorney-in-fact against an losses, claims,
damages or liabilities (or actions in these reports) that arise out of or are
based upon any untrue statements or omission of necessary facts in the
information provided by the undersigned to such attorney-in-fact for purposes of
executing, acknowledging, delivering or filing Forms 3, 4 or 5 (including
amendments thereto) or Form ID and agrees to reimburse the Company and such
attorney-in-fact for any legal or other expenses reasonably incurred in
connection with investigating or defending against any such loss, claim, damage,
liability or action.

     This Power of Attorney supersedes any power of attorney previously execute
by the undersigned regarding the purposes outlined in the first paragraph hereof
("Prior Powers of Attorney"), and the authority of the attorney-in-fact named in
any Prior Powers of Attorney is hereby revoked. Notwithstanding the foregoing,
the undersigned hereby ratifies and approves any actions taken pursuant to any
Prior Powers of Attorney for any of the purposes set forth herein, including
without limitation the granting thereof to any substitute attorney-in-fact.

     This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4, and 5 with respect to the
undersigned's holdings of and transactions in securities issued by the Company,
unless earlier revoked by the undersigned in a signed writing delivered to the
foregoing attorneys-in-fact.

     IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 19th day of January, 2024.

                                    Signature:   /s/ Azmi Nabulsi
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                                    Name:   Azmi Nabulsi
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