C3is Inc. (CISS) director Ioannis Kostogiannis files initial Form 3

Rhea-AI Filing Summary

C3is Inc. director Ioannis Kostogiannis filed an initial Form 3, which is a required report of insider holdings. The filing shows no reported purchases, sales, option exercises, gifts, or other equity transactions, indicating this is an administrative disclosure rather than a trading event.

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SEC 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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1. Name and Address of Reporting Person^*

Kostogiannis Ioannis

(Last) (First) (Middle)

C3IS INC.

331 KIFISSIAS AVENUE ERITHREA

(Street)

ATHENS GREECE 14561

(City) (State) (Zip)

GREECE

(Country)

2. Date of Event Requiring Statement (Month/Day/Year)
03/18/2026

3. Issuer Name and Ticker or Trading Symbol
C3is Inc. [ CISS ]

3a. Foreign Trading Symbol
[NONE]

5. If Amendment, Date of Original Filed (Month/Day/Year)

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

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)

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: 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

Explanation of Responses:

Remarks:

Exhibit 24 - Power of Attorney

No securities are beneficially owned.

	/s/ Nina Pyndiah, Attorney-in-Fact	03/18/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* 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).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 3: SEC 1473 (03-26)

FAQ

What does the C3is Inc. (CISS) Form 3 filing report?

The Form 3 reports director Ioannis Kostogiannis’s initial insider status at C3is Inc.. It is an administrative ownership filing, with no reported purchases, sales, or derivative transactions in the disclosed summary data.

Did Ioannis Kostogiannis buy or sell C3is Inc. (CISS) shares in this Form 3?

No, the Form 3 for Ioannis Kostogiannis shows zero buy and zero sell transactions. The transaction summary lists no purchases, sales, exercises, gifts, or other equity trades associated with this filing.

What role does Ioannis Kostogiannis have at C3is Inc. (CISS)?

Ioannis Kostogiannis is identified as a director of C3is Inc. in the Form 3. He is not listed as an officer and is not flagged as a ten percent owner in the provided insider data.

Are there any derivative securities reported in the C3is Inc. (CISS) Form 3?

No derivative positions are shown in the Form 3 for Ioannis Kostogiannis. The derivative summary is empty, and the transaction summary reports zero derivative transactions or option exercises in this filing.

Does the C3is Inc. (CISS) Form 3 indicate any gifts or tax-related share withholdings?

No, the Form 3 reports zero gifts and zero tax-withholding share dispositions. The transaction summary shows no restructuring, gifts, or other non-market movements of C3is Inc. equity for this reporting person.