As of November 6, 2026, 2 holders' latest Schedule 13D or 13G filings report owning 5% or more of Seanergy Maritime Holdings Corp. The largest reported stake is Tsantanis Stamatios', at 9.62%. 5 filings are on record since August 4, 2025 (Schedule 13D/A, March 31, 2026).
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Key facts
- · Reporting person: Konstantakopoulos Konstantinos · Sole voting: 0 · Shared voting: 1,063,079 · Sole dispositive: 0 · Shared dispositive: 1,063,079 · SCHEDULE 13G/A, 2026-09-21
- · Holder: Konstantakopoulos Konstantinos · Percent: 10.2% · SCHEDULE 13G/A
- · Holder: Tsantanis Stamatios · Percent: 9.62% · SCHEDULE 13D/A
- · Holder: George Economou · Percent: 8.8% · Shares: 1,848,534 · SCHEDULE 13D/A
- · Holder: Konstantakopoulos Konstantinos · Percent: 13.2% · SCHEDULE 13G/A
Seanergy Maritime Holdings Corp. has 5 Schedule 13D or 13G filings on record since 2025-08-04. 2 holders' latest filing reports 5% or more of common stock, par value $0.0001 per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| 9.62% | 2,084,403 | SCHEDULE 13D/A, 2026-03-31 | 2026-03-06 | |
| 8.8% | 1,848,534 | SCHEDULE 13D/A, 2026-03-16 | 2026-03-16 | |
| 4.9% | 1,063,079 | SCHEDULE 13G/A, 2026-09-21 | 2026-09-18 |
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More on Seanergy Maritime Holdings Corp. and the records around it.
Seanergy Maritime Holdings Corp. elsewhere on the record
Companies that share a holder
- Konstantakopoulos Konstantinos also filed stake reports on 1 other company: Costamare Bulkers Holdings Ltd (Oct 2025)
- Sphinx Investment Corp. also filed stake reports on 1 other company: OceanPal Inc. (Sep 2025)
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Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| Konstantakopoulos Konstantinos | 0 | 1,063,079 | 0 | 1,063,079 | SCHEDULE 13G/A, 2026-09-21 |
| Longshaw Maritime Investments S.A. | 0 | 1,063,079 | 0 | 1,063,079 | SCHEDULE 13G/A, 2026-09-21 |
The latest filing identifies Seanergy Maritime Holdings Corp. by CUSIP Y73760400 and gives its principal executive office as 154 Vouliagmenis Avenue, Glyfada (SCHEDULE 13G/A, 2026-09-21).
Purpose of Transaction (Item 4)
George Economou
Item 4 of the Initial 13D is hereby supplemented as set forth below. "As previously disclosed, on March 4, 2024, Sphinx, one of the Reporting Persons, commenced litigation in the Republic of the Marshall Islands against Stamatis Tsantanis, Christina Anagnostara, Dimitrios Anagnostopoulos, Elias Culucundis, Ioannis (John) Kartsonas and the Issuer by filing a complaint in the High Court of the Republic of the Marshall Islands (the "High Court"), seeking, among other things, to void and cancel the Series B Preferred Stock issued to Mr. Tsantanis, to cancel the certificate of designation for the Series B Preferred Stock, to prohibit Mr. Tsantanis from exercising the voting rights of the Series B Preferred Stock and to prohibit the Issuer from recognizing any such votes purportedly cast. The High Court rendered a decision in that case, dismissing Sphinx's complaint on the basis that Sphinx lacked standing to bring its claims, on October 28, 2024 and issued a corrected order amending that decision on October 30, 2024 and the Supreme Court of the Marshall Islands rendered a decision in the appeal of such case on February 20, 2026 affirming the High Court's dismissal. In light of the decision of the Supreme Court of the Marshall Islands, as of March 16, 2026, the Reporting Persons no longer intend to seek to change or influence the control of the Company or to change the Company's capital structure or corporate governance."Item 4 of the SCHEDULE 13D/A filed 2026-03-16
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-08-04 | Konstantakopoulos Konstantinos | 13.2% | SCHEDULE 13G/A |
| 2026-03-16 | George Economou | 8.8% | SCHEDULE 13D/A |
| 2026-03-31 | Tsantanis Stamatios | 9.62% | SCHEDULE 13D/A |
| 2026-04-08 | Konstantakopoulos Konstantinos | 10.2% | SCHEDULE 13G/A |
| 2026-09-21 | Konstantakopoulos Konstantinos | 4.9% | SCHEDULE 13G/A |
Questions about who owns Seanergy Maritime Holdings Corp.
Who owns Seanergy Maritime Holdings Corp.?
On this page, 2 holders' latest ownership filings report 5% or more of Seanergy Maritime Holdings Corp.: Tsantanis Stamatios (9.62%, Schedule 13D/A, filed 2026-03-31) and George Economou (8.8%, Schedule 13D/A, filed 2026-03-16).
Who are the largest shareholders of Seanergy Maritime Holdings Corp.?
By the share each holder's latest filing reports, the largest holders of Seanergy Maritime Holdings Corp. on this page are Tsantanis Stamatios (9.62%) and George Economou (8.8%).
When did Tsantanis Stamatios buy into Seanergy Maritime Holdings Corp.?
The filings give report dates, not purchase dates. The earliest filing from Tsantanis Stamatios on this page is the Schedule 13D/A, filed 2026-03-31, reporting 9.62%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 5 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
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Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.