Initial Statement of Beneficial Ownership (Form 3)

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * Smith William F. 2. Date of Event Requiring Statement (Month/Day/Year) 10/28/2025 3. Issuer Name and Ticker or Trading Symbol Terrestrial Energy Inc. /DE/ [IMSR] (Last) (First) (Middle) 2730 W. TYVOLA ROAD, SUITE 100 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Chief Operating Officer 5. If Amendment, Date Original Filed (Month/Day/Year) (Street) CHARLOTTE, NC 28217 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (Right to Buy)	(1)	05/02/2036	Common Stock	223,515	$1.1185(5)	D
Stock Option (Right to Buy)	(1)	02/06/2037	Common Stock	335,272	$1.4764(5)	D
Stock Option (Right to Buy)	(1)	08/01/2038	Common Stock	8,941	$2.0133	D
Stock Option (Right to Buy)	(2)	02/06/2039	Common Stock	447,030	$2.0133	D
Stock Option (Right to Buy)	(1)	01/27/2040	Common Stock	111,758	$2.0133	D
Stock Option (Right to Buy)	(1)	11/18/2040	Common Stock	223,515	$2.237	D
Stock Option (Right to Buy)	(1)	05/19/2042	Common Stock	89,406	$2.237	D
Stock Option (Right to Buy)	04/01/2024(3)	04/01/2043	Common Stock	156,461	$2.237	D
Stock Option (Right to Buy)	06/20/2027(4)	06/25/2045	Common Stock	134,109	$7.8295	D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
Smith William F. 2730 W. TYVOLA ROAD, SUITE 100 CHARLOTTE, NC 28217			Chief Operating Officer

Signatures

/s/ Steven M. Millsap, pursuant to Power of Attorney		11/07/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Consists of options granted pursuant to the Terrestrial Energy Inc. Second Amended and Restated 2024 Stock Option Plan. The options are currently exercisable.
(2)	Consists of options granted pursuant to the Terrestrial Energy Inc. Second Amended and Restated 2024 Stock Option Plan. The options vest based on certain specified milestone conditions.
(3)	Consists of options granted pursuant to the Terrestrial Energy Inc. Second Amended and Restated 2024 Stock Option Plan. The options vest in one-third increments on each of the first, second and third anniversaries of the grant date, subject to the reporting person's continued service through each applicable vesting date.
(4)	Consists of options granted pursuant to the Terrestrial Energy Inc. Second Amended and Restated 2024 Stock Option Plan. The options vest in one-half increments on June 20, 2027 and June 30, 2028.
(5)	Price is expressed in Canadian dollars.
Remarks: Exhibit List - Exhibit 24.1 - Power of Attorney

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