C3is investor Timothy Horne reports 9.07% stake

C3is Inc. (CISS) has a new significant shareholder disclosure, as Timothy P. Horne reported beneficial ownership of 135,000 shares of the company’s common stock.

Rhea-AI Filing Summary

C3is Inc. (CISS) has a new significant shareholder disclosure, as Timothy P. Horne reported beneficial ownership of 135,000 shares of the company’s common stock. This represents 9.07% of the outstanding common shares, all held with sole voting and dispositive power.

Key Figures

Shares beneficially owned: 135,000 shares Percent of class: 9.07% Sole voting power: 135,000 shares +3 more

6 metrics

Shares beneficially owned 135,000 shares Common Stock, no par value, reported as beneficially owned by Timothy P. Horne

Percent of class 9.07% Percentage of C3is Inc. common stock beneficially owned by Timothy P. Horne

Sole voting power 135,000 shares Shares over which Timothy P. Horne has sole power to vote or direct the vote

Shared voting power 0 shares Shares over which Timothy P. Horne has shared power to vote or direct the vote

Sole dispositive power 135,000 shares Shares over which Timothy P. Horne has sole power to dispose or direct disposition

Shared dispositive power 0 shares Shares over which Timothy P. Horne has shared power to dispose or direct disposition

Key Terms

beneficially owned, sole voting power, dispositive power

3 terms

beneficially owned financial

"Ownership (a) | Amount beneficially owned: 135,000"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole voting power financial

"Sole power to vote or to direct the vote: 135,000"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

dispositive power financial

"Sole power to dispose or to direct the disposition of: 135,000"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What percentage of C3is Inc. (CISS) does Timothy P. Horne beneficially own?

Timothy P. Horne beneficially owns 9.07% of C3is Inc.’s common stock. This percentage is based on his reported holdings of 135,000 shares of common stock with sole voting and dispositive power.

How many C3is Inc. (CISS) shares does Timothy P. Horne report owning?

Timothy P. Horne reports beneficial ownership of 135,000 shares of C3is Inc. common stock. All of these shares are held with sole power to vote and sole power to dispose.

Does Timothy P. Horne share voting or dispositive power over his C3is Inc. (CISS) shares?

No. The filing states that Timothy P. Horne has sole voting power over 135,000 shares and sole dispositive power over 135,000 shares, with zero shares subject to shared voting or shared dispositive power.

What class of C3is Inc. (CISS) securities is covered by this Schedule 13G?

The Schedule 13G covers C3is Inc. Common Stock, no par value. Timothy P. Horne’s beneficial ownership relates solely to this class of securities.

Who is the reporting person in this C3is Inc. (CISS) Schedule 13G and what is his citizenship?

The reporting person is Timothy P. Horne. The filing identifies his citizenship as the United States and lists his principal office or residence in Rye, New Hampshire.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/03/2026 - 10:07 AM EDT Accepted by SEC EDGAR 09/03/2026 - 10:06 AM EDT Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

C3is Inc.

(Name of Issuer)

Common Stock, no par value

(Title of Class of Securities)

Y18284409

(CUSIP Number)

08/27/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): Y18284409

1

Names of Reporting Persons

HORNE TIMOTHY P

2

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

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

NEW HAMPSHIRE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 135,000.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 135,000.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

135,000.00

10

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

11

Percent of class represented by amount in row (9)

9.1 %

12

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: C3is Inc.
(b)	Address of issuer's principal executive offices: 331 KIFISSIAS AVENUE, ERITHREA, ATHENS, GREECE, 14561.
Item 2.
(a)	Name of person filing: Timothy P. Horne
(b)	Address or principal business office or, if none, residence: 41 Straws Point, Rye, New Hampshire 03870
(c)	Citizenship: United States
(d)	Title of class of securities: Common Stock, no par value
(e)	CUSIP Number(s): Y18284409
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: 135,000
(b)	Percent of class: 9.07 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 135,000
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 135,000
	(iv) Shared power to dispose or to direct the disposition of: 0
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.
	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.

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.

HORNE TIMOTHY P

Signature:	Timothy P Horne
Name/Title:	Timothy P. Horne
Date:	09/03/2026