SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Terrestrial Energy Inc.

(Name of Issuer)

Common Stock, par value $0.0001 per share

(Title of Class of Securities)

881454102

(CUSIP Number)

10/29/2025

(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)

SCHEDULE 13G

CUSIP No.

881454102

Names of Reporting Persons

Roberto Marco Sella

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 719,433.00
6	Shared Voting Power 14,659,256.00
7	Sole Dispositive Power 719,433.00
8	Shared Dispositive Power 14,659,256.00

Aggregate Amount Beneficially Owned by Each Reporting Person

15,378,689.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

14.34 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person: Based on 81,771,423 shares of common stock, par value $0.0001 per share ("Shares"), of Terrestrial Energy Inc., a Delaware corporation, (the "Issuer") outstanding as of December 15, 2025 and 24,011,029 Shares issuable upon the conversion of common shares and preferred shares of Terrestrial Energy Canada (Exchange) Inc. ("Exchange Shares"), as disclosed in Amendment No. 1 to the Issuer's Registration Statement on Form S-1 (File No. 333-291796) as declared effective by the Securities Exchange Commission (the "Commission") on December 23, 2025. The aggregation of the outstanding Shares and the Exchange Shares is based solely upon statements and disclosures made by the Issuer.

SCHEDULE 13G

CUSIP No.

881454102

Names of Reporting Persons

Roberto M. Sella 2012 Family Trust

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

PENNSYLVANIA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,538,319.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,538,319.00

Aggregate Amount Beneficially Owned by Each Reporting Person

1,538,319.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

1.44 %

Type of Reporting Person (See Instructions)

Comment for Type of Reporting Person: Based on 81,771,423 Shares of the Issuer outstanding as of December 15, 2025 and 24,011,029 Shares issuable upon the conversion of the Exchange Shares, as disclosed in Amendment No. 1 to the Issuer's Registration Statement on Form S-1 (File No. 333-291796) as declared effective by the Commission on December 23, 2025. The aggregation of the outstanding Shares and the Exchange Shares is based solely upon statements and disclosures made by the Issuer.

SCHEDULE 13G

CUSIP No.

881454102

Names of Reporting Persons

LL Charitable Foundation

Check the appropriate box if a member of a Group (see instructions)

(a)

(b)

Sec Use Only

Citizenship or Place of Organization

PENNSYLVANIA

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 653,334.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 653,334.00

Aggregate Amount Beneficially Owned by Each Reporting Person

653,334.00

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

Checkbox not checked

Percent of class represented by amount in row (9)

0.62 %

Type of Reporting Person (See Instructions)

SCHEDULE 13G

Item 1.

(a)

Name of issuer:

Terrestrial Energy Inc.

(b)

Address of issuer's principal executive offices:

2730 W. Tyvola Road, Suite 100, Charlotte, NC 28217

Item 2.

(a)

Name of person filing:

This statement is filed on behalf of the following persons (collectively, the "Reporting Persons"): (i) Roberto Sella, an individual; (ii) Roberto M. Sella 2012 Family Trust, (the "Trust"); and (iii) LL Charitable Foundation (the "Foundation"). This Statement relates to Common Stock, par value $0.0001 per share (the "Shares") of the Issuer held by Roberto Sella, the Trust, and the Foundation. Mr. Sella is a principal owner and controlling person of the Trust and the Foundation, and in such capacity, may be deemed to beneficially own the Shares held by the Trust and the Foundation, respectively.

(b)

Address or principal business office or, if none, residence:

2400 Market Street, Suite 302 Philadelphia, PA, 19103

(c)

Citizenship:

(i) Roberto Sella, is a United States citizen; (ii) the Trust is organized under the laws of Pennsylvania; and (iii) the Foundation is organized under the laws of Pennsylvania.

(d)

Title of class of securities:

Common Stock, par value $0.0001 per share

(e)

CUSIP No.:

881454102

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:

(a)

Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);

(b)

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);

(c)

Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);

(d)

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);

(e)

An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f)

An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g)

A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h)

A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

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

(k)

Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

Item 4.

Ownership

(a)

Amount beneficially owned:

The Reporting Persons held securities of Terrestrial Energy Inc., a Delaware corporation ("Old Terrestrial"). On October 29, 2025, Old Terrestrial consummated a business combination with the Issuer (the "Business Combination"), and the Reporting Persons received securities of the Issuer at the closing of the Business Combination. The securities reported on this statement include (i) 180,316 Shares held directly by Mr. Sella; (ii) 539,117 Shares issuable upon the exercise of warrants held by Mr. Sella, having an exercise price of $2.24 per share; (iii) 12,244,088 Shares held jointly by Mr. Sella and Mr. Sella's spouse (iv) 223,515 Shares issuable upon the exercise of warrants held jointly by Mr. Sella and his spouse, having an exercise price of $2.24 per share; (v) 807,873 Shares held by the Trust; (vi) 730,446 Shares issuable upon the exercise of warrants held by the Trust, having an exercise price of $2.24 per share; and (vii) 653,334 Shares held by the Foundation.

(b)

Percent of class:

The following percentages are based on 81,771,423 Shares of the Issuer outstanding as of December 15, 2025 and 24,011,029 Shares issuable upon the conversion of the Exchange Shares. The aggregation of the outstanding Shares and the Exchange Shares is based solely upon statements and disclosures made by the Issuer. (i) Mr. Sella: 12.38% (ii) the Trust: 1.44% (iii) the Foundation: 0.62%

(c)

Number of shares as to which the person has:

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

(i) Mr. Sella: 719,433 (ii) the Trust: 0 (iii) the Foundation 0

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

(i) Mr. Sella: 14,659,256 (ii) the Trust: 1,538,319 (iii) the Foundation: 653,334

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

(i) Mr. Sella: 719,433 (ii) the Trust: 0 (iii) the Foundation 0

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

(i) Mr. Sella: 14,659,256 (ii) the Trust: 1,538,319 (iii) the Foundation: 653,334

Item 5.

Ownership of 5 Percent or Less of a Class.

Not Applicable

Item 6.

Ownership of more than 5 Percent on Behalf of Another Person.

If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.

See items 2 and 4 of this statement for more information.

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.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Roberto Marco Sella

Signature:	/s/ Roberto Sella
Name/Title:	Roberto Sella
Date:	01/22/2026

Roberto M. Sella 2012 Family Trust

Signature:	/s/ Roberto Sella
Name/Title:	Roberto Sella, as Authorized Party
Date:	01/22/2026

LL Charitable Foundation

Signature:	/s/ Roberto Sella
Name/Title:	Roberto Sella, its President and Director
Date:	01/22/2026

Exhibit Information

99.1 Joint Filing Statement

SEC Form SCHEDULE 13G filed by Terrestrial Energy Inc.