Comparable stake leader
Imperial Petroleum Inc./Marshall Islands
SEC ownership of C3is Inc.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001951067.
Disclosed value leader
Athanasios Tsiakmakis
Comparable rows
15/15
Latest evidence
18 May 2026
- Public ticker
- CISS on Nasdaq
- Parsed ownership sources
- 13D/G, 3/4/5, and 13F
- Largest SEC-reported holder
- Imperial Petroleum Inc./Marshall Islands
- Latest 13D/G holder
- Imperial Petroleum Inc./Marshall Islands
- Latest parsed ownership date
- 18 May 2026
- Issuer CIK
- 0001951067
- Issuer location
- Athens, Greece
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
2 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of C3is Inc. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
Imperial Petroleum Inc./M...
Disclosed value leader
Athanasios Tsiakmakis
Comparable rows
15/15
Latest evidence
18 May 2026
13D/G
3/4/5
13F
Lead comparable stake: 90%
13D/G row: Imperial Petroleum Inc./Marshall Islands
Showing 1-8 of 15 holder rows.
Quick read
Imperial Petroleum Inc./Marshall Islands leads the comparable SEC ownership view at 90%.
15 of 15 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens Imperial Petroleum Inc./Marshall Islands's linked filing trail.
Comparable ownership
Top 5
Imperial Petroleum Inc./Marshall ...
90%
L1 Capital Global Opportunities M...
10%
S.H.N. Financial Investments Ltd.
10%
Ayrton Capital LLC
10%
WEXFORD CAPITAL LP
7%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 15 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| Imperial Petroleum Inc./Marshall Islands |
13D/G
Imperial Petroleum Inc.
|
90%
|
—
4,994,672 shares
|
$0 | 04 May 2026 |
| L1 Capital Global Opportunities Master Fund, Ltd. |
13D/G
|
10%
|
$651,523
443,213 shares
|
$0 | 11 Dec 2025 |
| S.H.N. Financial Investments Ltd. |
13D/G
|
10%
|
$651,523
443,213 shares
|
+$542,486 | 11 Dec 2025 |
| Ayrton Capital LLC |
13D/G
|
10%
|
—
856,228 shares
|
$0 | 31 Dec 2025 |
| WEXFORD CAPITAL LP |
13D/G
|
7%
|
—
112,014 shares
|
$0 | 19 Sep 2025 |
| TOWERVIEW LLC |
13D/G
|
6.5%
|
$4,900
35,000 shares
|
$0 | 18 May 2026 |
| Alta Partners LLC |
13D/G
|
5.2%
|
$80,893
56,176 shares
|
$0 | 27 Feb 2026 |
| Athanasios Tsiakmakis |
13D/G
|
5%
|
$688,000
400,000 shares
|
+$421,400 | 09 Jan 2026 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Insider buy and sell flow is broadly balanced over the last 12 months. No Buy or Sell transactions have been reported since 05 Jun 2025.
Buys
$0
Insiders: 0
Sells
$0
Insiders: 0
Net
$0
Shares: 0
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 0
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 0 | $0 | $0 | $0 |
| 3-6 | 0 | 0 | $0 | $0 | $0 |
| 6-9 | 0 | 0 | $0 | $0 | $0 |
| 9-12 | 0 | 0 | $0 | $0 | $0 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-5 of 5 reporting-owner rows connected to C3is Inc.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
5
Largest Forms 3/4/5 holder
Harry Vafias
Net 12M change
$0
Latest report
18 Mar 2026
| Name | Relationship | Holdings Value | Past Year Net Change | Change % | Valuation | Report Date |
|---|---|---|---|---|---|---|
| Harry Vafias | Director | $668 | Market | 18 Mar 2026 | ||
| Adamantios Andriotis | CEO and President, Director | Mixed | 18 Mar 2026 | |||
| Nina Sarojini Pyndiah | Chief Financial Officer | Mixed | 18 Mar 2026 | |||
| Georgios Xiradakis | Director | Mixed | 18 Mar 2026 | |||
| Ioannis Kostogiannis | Director | Mixed | 18 Mar 2026 |
Recent insider transactions for C3is Inc.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| Harry Vafias | CISS | Common Stock | 0 | 3,616 | 18 Mar 2026 | By Arethusa Properties LTD | ||||
| Harry Vafias | CISS | Common Stock | 0 | 1,162 | 18 Mar 2026 | Direct |
* marks a reported price that did not pass the local price check.