United States securities and exchange commission logo

                            March 19, 2021

       Eli Casdin
       Chief Executive Officer
       CM Life Sciences III Inc.
       c/o Corvex Management LP
       667 Madison Avenue
       New York, NY 10065

                                                        Re: CM Life Sciences
III Inc.
Statement on Form S-1
                                                            Filed February 25,
                                                            File No. 333-253475

       Dear Mr. Casdin:

              We have reviewed your registration statement and have the
following comment. In our
       comment, we may ask you to provide us with information so we may better
understand your

              Please respond to this letter by amending your registration
statement and providing the
       requested information. If you do not believe our comment applies to your
facts and
       circumstances or do not believe an amendment is appropriate, please tell
us why in your

              After reviewing any amendment to your registration statement and
the information you
       provide in response to this comment, we may have additional comments.

       Registration Statement on Form S-1

       Proposed Business
       Sourcing of Potential Initial Business Combination Targets, page 88

   1.                                                   We note that affiliates
of management are currently searching for an acquisition target in
                                                        the Life Sciences
industry sector in connection with the CM Life Sciences II, Inc. SPAC.
                                                        We also note your
statement that you "do not believe that any such potential conflicts
                                                        would materially affect
[your] ability to complete an initial business combination."
                                                        Expand your disclosure
here and elsewhere to address the reasons why you believe so, and
                                                        whether you would
expect CM Life Sciences II, Inc. to announce an acquisition target
                                                        before a target is
announced for the company.
 Eli Casdin
CM Life Sciences III Inc.
March 19, 2021
Page 2

        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.

       Refer to Rules 460 and 461 regarding requests for acceleration. Please
allow adequate
time for us to review any amendment prior to the requested effective date of
the registration

        You may contact Kathryn Jacobson, Staff Accountant, at (202) 551-3365
or Robert
Littlepage, Accounting Branch Chief, at (202) 551-3361 if you have questions
comments on the financial statements and related matters. Please contact Jeff
Kauten, Staff
Attorney, at (202) 551-3447 or Larry Spirgel, Office Chief, at (202) 551-3815
with any other

FirstName LastNameEli Casdin
                                                           Division of
Corporation Finance
Comapany NameCM Life Sciences III Inc.
                                                           Office of Technology
March 19, 2021 Page 2
cc:       Colin Diamond, Esq.
FirstName LastName