Terrestrial Energy Inc. /DE/

As filed with the U.S. Securities and Exchange Commission on November 25, 2025

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORMS-1 REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

TERRESTRIAL ENERGY INC.

(Exact name of registrant as specified in its charter)

2730 W. Tyvola Road, Suite 100

Charlotte, NC 28217

(646) 687-8212

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Simon Irish

Chief Executive Officer

2730 W. Tyvola Road, Suite 100

Charlotte, NC 28217

(646) 687-8212

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Eliot Robinson

Tyler Mark

Bryan Cave Leighton Paisner LLP

One Atlantic Center, 14th Floor,

1201 W. Peachtree St., N.W.,

Atlanta, GA 30309-3471

(404) 572-6600

**Approximate date of commencement of proposed sale to the public:**From time to time after this registration statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933 check the following box:☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering:☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering:☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering:☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act:

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act:☐

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act or until this registration statement shall become effective on such date as the SEC, acting pursuant to said Section 8(a), may determine**.**

The information in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the U.S. Securities and Exchange Commission is effective. The preliminary prospectus is not an offer to sell these securities and does not constitute the solicitation of offers to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED NOVEMBER 25, 2025

TERRESTRIAL ENERGY INC.

Primary Offering of up to

18,776,119 SHARES OF COMMON STOCK

Secondary Offering of up to

13,117,599 SHARES OF COMMON STOCK

1,267,599 WARRANTS TO PURCHASE SHARES OF COMMON STOCK

This prospectus relates to the offer and sale by Terrestrial Energy Inc., a Delaware corporation (“us,” “we,” “New Terrestrial Energy,” or the “Company”) of (i) up to 8,117,599 shares of common stock, par value $0.0001 per share, of the Company (the “New Terrestrial Common Shares”) that are issuable by us upon the exercise of Private Placement Warrants (as defined below); and (ii) up to 10,658,520 New Terrestrial Common Shares that are issuable by us upon the exercise of Legacy Terrestrial Warrants (as defined below) of Terrestrial Energy Holdings, a Delaware corporation and wholly owned subsidiary of the Company (“Legacy Terrestrial Energy”) that were assumed by New Terrestrial Energy pursuant to the Business Combination Agreement.

This prospectus also relates to the offer and resale from time to time by the selling securityholders (including their transferees, donees, pledgees and other successors-in-interest) named in this prospectus (the “Selling Securityholders”) entitled to resale registration rights pursuant to the Amended and Restated Registration Rights Agreement, dated as of October 28, 2025 (the “Registration Rights Agreement”) or other agreements, of up to:

We are registering the offer and sale and/or resale of these securities to satisfy certain registration obligations we have and certain registration rights we have granted. The Selling Securityholders may offer all or part of the Resale Securities for resale from time to time through public or private transactions, at either prevailing market prices or at privately negotiated prices. The Resale Securities are being registered to permit the Selling Securityholders to sell Resale Securities from time to time, in amounts, at prices and on terms determined at the time of offering. The Selling Securityholders may sell the Resale Securities through ordinary brokerage transactions, in underwritten offerings, directly to market makers of our securities or through any other means described in the section entitled “Plan of Distribution” herein. In connection with any sales of Resale Securities offered hereunder, the Selling Securityholders, any underwriters, agents, brokers or dealers participating in such sales may be deemed to be “underwriters” within the meaning of the Securities Act, or the Exchange Act. We are registering the Resale Securities for resale by the Selling Securityholders, or their donees, pledgees, transferees, distributees or other successors-in-interest selling our New Terrestrial Common Shares or Private Placement Warrants or interests in our New Terrestrial Common Shares or Private Placement Warrants received after the date of this prospectus from the Selling Securityholders as a gift, pledge, partnership distribution or other transfer.

Certain Resale Securities held by the Selling Securityholders party to the Registration Rights Agreement are subject to lock-up restrictions that prohibit them from selling such securities at this time, subject to certain exceptions. See the section of this prospectus entitled “Description of Securities.”

Some of the New Terrestrial Common Shares being registered for resale were acquired by the Selling Securityholders for prices considerably below the current market price of the New Terrestrial Common Shares. The current market price ($9.62 closing price on November 21, 2025) is below the $10.00 per unit price offered in HCM II’s initial public offering, however, certain Selling Securityholders may have an incentive to sell because they have purchased their New Terrestrial Common Shares or Private Placement Warrants at effective prices significantly lower than our public investors or the current trading price of the New Terrestrial Common Shares or Public Warrants and may profit significantly so even under circumstances in which our public securityholders or certain other Selling Securityholders would experience losses in connection with their investment. For additional information, see “Risk Factors — Risks Relating to Ownership of Our Securities — Certain of the Selling Securityholders acquired their New Terrestrial Common Shares at a price that is less than the market price of the New Terrestrial Common Shares as of the date of this prospectus, may earn a positive rate of return even if the price of the New Terrestrial Common Shares declines and may be willing to sell their New Terrestrial Common Shares at a price less than stockholders that acquired New Terrestrial Common Shares in the public market.”

As of November 21, 2025, we had 105,782,452 New Terrestrial Common Shares and share equivalents outstanding, consisting of 81,771,423 New Terrestrial Common Shares issued and outstanding as well as 24,011,029 New Terrestrial Common Shares that would be issued and outstanding upon the exchange of outstanding Exchangeable Shares (as defined below) of a subsidiary, which are convertible into New Terrestrial Common Shares. “Fully diluted” ownership information gives effect to the issuance of 19,617,599 New Terrestrial Common Shares upon exercise of all outstanding Private Placement Warrants and Public Warrants (as defined below), 10,658,520 New Terrestrial Common Shares issuable upon the exercise of all outstanding Legacy Terrestrial Warrants, and 24,011,029 New Terrestrial Common Shares that would be issued and outstanding upon the exchange of outstanding Exchangeable Shares.

The New Terrestrial Common Shares being offered for resale by the Selling Securityholders pursuant to this prospectus represent approximately 9.7% of our total issued and outstanding New Terrestrial Common Shares on a fully diluted basis, and the Private Placement Warrants being offered for resale pursuant to this prospectus represent approximately 4.2% of our current total outstanding Warrants. Upon expiration of the contractual lock-up restrictions mentioned above and described in the section entitled “Certain Relationships and Related Persons Transactions,” the Selling Securityholders, including Shawn Matthews, one of our directors (who would hold approximately 1.7% of our total issued and outstanding New Terrestrial Common Shares on a fully diluted basis calculated in the manner set forth above), will be able to sell all of their Resale Securities registered for resale hereunder for so long as this registration statement of which this prospectus forms a part is available for use. Given the substantial number of Resale Securities being registered for potential resale by the Selling Securityholders pursuant to the registration statement of which this prospectus forms a part, the sale of such Resale Securities by the Selling Securityholders, or the perception in the market that the Selling Securityholders may or intend to sell all or a significant portion of such Resale Securities, could increase the volatility of the market price of our New Terrestrial Common Shares or Public Warrants or result in a significant decline in the public trading price of our New Terrestrial Common Shares or Public Warrants. The Selling Securityholders acquired, or have the option to acquire, the New Terrestrial Common Shares covered by this prospectus at prices ranging from less than $0.01 per share to $11.50 per share. By comparison, the closing price per share as of November 21, 2025 was $9.62 per share and the offering price to public stockholders in HCM II’s IPO was $10.00 per unit, each of which consisted of one Ordinary Share and one-half of one redeemable public warrant of HCM II. Consequently, certain Selling Securityholders may realize a positive rate of return on the sale of their Resale Securities covered by this prospectus even if the market price of New Terrestrial Common Shares decreases below the current market price or remains below the $10.00 per unit price offered in the HCM II IPO and public stockholders and/or warrantholders may experience a negative rate of return on their investment.

We will not receive any proceeds from the sale of the Resale Securities by the Selling Securityholders. We will receive the proceeds upon exercise of New Terrestrial Warrants or Legacy Terrestrial Warrants to the extent such New Terrestrial Warrants or Legacy Terrestrial Warrants are exercised for cash. Assuming the exercise of all outstanding New Terrestrial Warrants for cash, we would receive aggregate proceeds of approximately $225.6 million. However, we will only receive such proceeds if all New Terrestrial Warrant holders fully exercise their Warrants for cash. The exercise price of the New Terrestrial Warrants is $11.50 per share. Assuming the exercise of all outstanding Legacy Terrestrial Warrants for cash, we would receive aggregate proceeds of approximately $23.9 million. However, we will only receive such proceeds if all Legacy Terrestrial Warrant holders fully exercise their Warrants for cash. The exercise price of the Legacy Terrestrial Warrants is $2.24 per share. We believe that the likelihood that holders determine to exercise their Warrants, and therefore the amount of cash proceeds that we would receive, is dependent upon the market price of our New Terrestrial Common Shares. If the market price for our New Terrestrial Common Shares is less than the exercise price of the New Terrestrial Warrants or Legacy Terrestrial Warrants (on a per share basis), as applicable, we believe that holders will be very unlikely to exercise any of their New Terrestrial Warrants or Legacy Terrestrial Warrants, as applicable, and accordingly, we will not receive any such proceeds. There is no assurance that the New Terrestrial Warrants or Legacy Terrestrial Warrants will be or will remain “in the money” prior to their expiration or that the holders will exercise their Warrants. Holders of New Terrestrial Warrants and New Terrestrial Warrants have the option to exercise their respective warrants on a cashless basis in accordance with the terms of the Warrant Agreement and the Legacy Terrestrial Warrants (as applicable). To the extent that any warrants are exercised on a cashless basis, the amount of cash we would receive from the exercise of such warrants will decrease.

We will bear all costs, expenses, and fees in connection with the registration of the New Terrestrial Common Shares and Private Placement Warrants. The Selling Securityholders will bear all commissions and discounts, if any, attributable to their respective sales of the New Terrestrial Common Shares and Private Placement Warrants.

Our New Terrestrial Common Shares and Public Warrants are listed on the Nasdaq Stock Market LLC (“Nasdaq”) under the symbols “IMSR” and “IMSRW,” respectively. On November 21, 2025, the closing price of our New Terrestrial Common Shares was $9.62 per share and the closing price for our Public Warrants was $3.26 per warrant.

We are an “emerging growth company” and a “smaller reporting company” under the federal securities laws and will be subject to reduced disclosure and public reporting requirements. See “Summary — Implications of Being an Emerging Growth Company and a Smaller Reporting Company.”

Investing in shares of our securities involves risks that are described in the “Risk Factors” section beginning on page12** of this prospectus.**

Neither the U.S. Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued under this prospectus or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is , 2025.