UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

SCHEDULE 13G

(Rule 13d-102)

Information to be Included in Statements Filed Pursuant

to § 240.13d-1(b), (c) and (d) and Amendments Thereto Filed

Pursuant to § 240.13d-2

Under the Securities Exchange Act of 1934

(Amendment No.     )

Third Harmonic Bio, Inc.

(Name of Issuer)

Common Stock, $0.0001

par value per share

(Title of Class of Securities)

88427A107

(CUSIP Number)

September 19, 2022

(Date of Event Which Requires Filing of This Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

☐ Rule 13d-1(b)

☒ Rule 13d-1(c)

☐ Rule 13d-1(d)

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934, as amended (“Act”), or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

Item 1(a).  Name of Issuer

The name of the issuer to which this filing on Schedule 13G relates is Third Harmonic Bio, Inc. (the “Issuer”).

Item 1(b).  Address of Issuer’s Principal Executive Offices

The principal executive offices of the Issuer are located at 300 Technology Square, 8th Floor, Cambridge, Massachusetts 02139.

Item 2(a).  Name of Person Filing

This Schedule 13G is being filed by Bain Capital Life Sciences Opportunities III, LP, a Delaware limited partnership (“BCLS III Opportunities”).

Bain Capital Life Sciences Investors, LLC, a Delaware limited liability company (“BCLSI”), is the manager of Bain Capital Life Sciences Opportunities III GP, LLC, a Delaware limited liability company (“BCLS III Opportunities GP” and, together with BCLS III Opportunities and BCLSI, the “Bain Capital Life Sciences Entities”), which is the general partner of BCLS III Opportunities. As a result, BCLSI may be deemed to share voting and dispositive power with respect to the securities held by BCLS III Opportunities.

BCLS III Opportunities and BCLSI have entered into a Joint Filing Agreement, dated September 29, 2022, pursuant to which they have agreed to file this Schedule 13G jointly in accordance with the provisions of Rule 13d-1(k)(1) promulgated under the Act.

Item 2(b).  Address of Principal Business Office or, if None, Residence

The principal business address for each of the Bain Capital Life Sciences Entities is 200 Clarendon Street, Boston, Massachusetts 02116.

Item 2(c).  Citizenship

Each of the Bain Capital Life Sciences Entities are organized under the laws of the State of Delaware.

Item 2(d).  Title of Class of Securities

The class of securities of the Issuer to which this Schedule 13G relates is Common Stock, $0.0001 par value per share (“Common Stock”).

Item 2(e).  CUSIP Number

The CUSIP number of the Common Stock is 88427A107.

Item 3.  If this statement is filed pursuant to §§ 240.13d-1(b), or 240.13d-2(b) or (c), check whether the person filing is a

If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution.

Item 4.  Ownership

(a) Amount beneficially owned:

As of the date hereof, BCLS III Opportunities holds 2,280,082 shares of Common Stock, representing approximately 5.7% of the outstanding shares of Common Stock.

The percentage of the outstanding shares of Common Stock held by BCLS III Opportunities is based on 40,328,935 shares of Common Stock issued and outstanding, as reported by the Issuer in its prospectus relating to its initial public offering, filed with the Securities and Exchange Commission pursuant to Rule 424(b) under the Securities Act of 1933, as amended, on September 15, 2022, after giving effect to the full exercise of the underwriters’ option to purchase additional shares of Common Stock.

(b) Percent of class:

See Item 4(a) hereof.

(c) Number of shares as to which the person has:

(i) Sole power to vote or to direct the vote:

0

(ii) Shared power to vote or direct the vote:

2,280,082

(iii) Sole power to dispose or to direct the disposition of:

0

(iv) Shared power to dispose or to direct the disposition of:

2,280,082

Item 5.  Ownership of Five Percent or Less of a Class

Not applicable.

Item 6.  Ownership of More than Five Percent on Behalf of Another Person

Not applicable.

Item 7.  Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person

Not applicable.

Item 8.  Identification and Classification of Members of the Group

Not applicable.

Item 9.  Notice of Dissolution of Group

Not applicable.

Item 10.  Certifications

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the Issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURES

After reasonable inquiry and to the best of its knowledge and belief, the undersigned certifies that the information in this statement is true, complete and correct.

Exhibit A

AGREEMENT REGARDING THE JOINT FILING OF

SCHEDULE 13G

The undersigned hereby agree as follows: