United States securities and exchange commission logo

                          August 11, 2023

       Eric Shaff
       President and Chief Executive Officer
       Seres Therapeutics, Inc.
       200 Sidney Street     4th Floor
       Cambridge, MA 02139

                                                        Re: Seres Therapeutics,
Statement on Form S-3
                                                            Filed August 8,
                                                            File No. 333-273794

       Dear Eric Shaff:

              This is to advise you that we have not reviewed and will not
review your registration

               Please refer to Rules 460 and 461 regarding requests for
acceleration. We remind you
       that the company and its management are responsible for the accuracy and
adequacy of their
       disclosures, notwithstanding any review, comments, action or absence of
action by the staff.

                                                        Please contact Alan
Campbell at 202-551-4224 with any questions.


                          Division of Corporation Finance

                          Office of Life Sciences
       cc:                                              Jennifer A. Yoon, Esq.