United States securities and exchange commission logo May 15, 2023 Andrew Obenshain President and Chief Executive Officer bluebird bio, Inc. 455 Grand Union Boulevard Somerville, MA 02145 Re: bluebird bio, Inc. Registration Statement on Form S-3 Filed May 9, 2023 File No. 333-271772 Dear Andrew Obenshain: 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: Wesley C. Holmes, Esq.