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, Inc. Registration Statement on Form S-3 Filed August 8, 2023 File No. 333-273794 Dear Eric Shaff: This is to advise you that we have not reviewed and will not review your registration statement. 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. Sincerely, Division of Corporation Finance Office of Life Sciences cc: Jennifer A. Yoon, Esq.