Castellum, Inc.
Castellum, Inc. (CTM) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · CTM · as of Sep 30, 2025
Ownership Breakdown
42
Institutional Holders
▲ 9 vs Q2
$9.27M
Total Inst. Value
▲ $1.97M vs Q2
94.70M
Shares Outstanding
freeFloat 78.59%
8.51M
13F Shares Held
▲ 1.55M vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
CTM largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
ESSEX INVESTMENT MANAGEMENT CO LLC services-management consulting services | 2.15M | 2.47% | 2.47% | $2.35B | Nov 6, 2025 | ▲ 63.1K |
VANGUARD GROUP INC services-management consulting services | 1.28M | 1.47% | 1.47% | $1.39B | Nov 7, 2025 | ▲ 225.9K |
GEODE CAPITAL MANAGEMENT, LLC services-management consulting services | 723.5K | 83.03% | 83.03% | $788.89M | Nov 12, 2025 | ▲ 124.3K |
MERIDIAN WEALTH MANAGEMENT, LLC services-management consulting services | 684.6K | 78.56% | 78.56% | $746.21M | Nov 4, 2025 | ▲ 67.8K |
LEGATO CAPITAL MANAGEMENT LLC services-management consulting services | 621.4K | 71.31% | 71.31% | $677.34M | Nov 12, 2025 | — held |
GOLDMAN SACHS GROUP INC services-management consulting services | 368.6K | 42.30% | 42.30% | $401.81M | Nov 14, 2025 | NEW |
BANK OF NEW YORK MELLON CORP services-management consulting services | 350.0K | 40.16% | 40.16% | $381.50M | Nov 3, 2025 | ▼ 150.0K |
JANE STREET GROUP, LLC services-management consulting services | 335.7K | 38.52% | 38.52% | $365.92M | Nov 14, 2025 | ▲ 141.0K |
STATE STREET CORP services-management consulting services | 303.9K | 34.87% | 34.87% | $331.25M | Nov 14, 2025 | ▲ 147.9K |
BLACKROCK, INC. services-management consulting services | 265.5K | 30.47% | 30.47% | $289.38M | Nov 12, 2025 | ▲ 138.1K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
18
Increased
+1.22M shares12
New Positions
first time holders4
Decreased
−220.6K shares5
Sold Out
fully exitedNet shares change (top 50)
+1.00M
+1.22M / −220.6K
Net new holders
+21
12 new / 5 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
CTM insider trading · insider activity
Source: SEC Form 4
Insiders have been primarily selling shares recently. Selling may be driven by pre-scheduled Rule 10b5-1 plans rather than negative sentiment.
0
Buy transactions
1
Sell transactions
0.00
Buy/Sell ratio
$2M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
MARTIN TAMMY L General Counsel and Secretary | Mar 31, 2026 | Award | 1,329 | $0.45 | $603.898 | 13.8K | Form 4 ↗ |
Bell David T Chief Financial Officer | Mar 31, 2026 | Award | 1,329 | $0.45 | $603.898 | 16.1K | Form 4 ↗ |
Merriman Andrew Chief Operating Officer | Mar 31, 2026 | Award | 1,329 | $0.45 | $603.898 | 537.3K | Form 4 ↗ |
McMillen Charles Thomas director | Mar 25, 2026 | Sale | 30,000 | $0.70 | $21.1K | 231.0K | Form 4 ↗ |
Ives Glen R President | Mar 27, 2026 | Purchase | 2,000 | $0.62 | $1.2K | 199.6K | Form 4 ↗ |
Merriman Andrew Chief Operating Officer | Mar 27, 2026 | Purchase | 2,000 | $0.64 | $1.3K | 536.0K | Form 4 ↗ |
Ives Glen R President | Mar 26, 2026 | Purchase | 10,000 | $0.66 | $6.6K | 197.6K | Form 4 ↗ |
McMillen Charles Thomas director | Mar 18, 2026 | Sale | 55,000 | $0.80 | $44.1K | 261.0K | Form 4 ↗ |
Merriman Andrew Chief Operating Officer | Mar 18, 2026 | Purchase | 3,000 | $0.80 | $2.4K | 534.0K | Form 4 ↗ |
WRIGHT JAY O General Counsel, Secretary | Dec 19, 2025 | Sale | 30,000 | $1.05 | $31.5K | 7.13M | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Castellum, Inc. (CTM) is primarily owned by institutional investors, who hold approximately 9.0% of total shares outstanding. Company insiders own approximately 21.41%, while retail and public investors account for the remaining 69.61%.
The largest institutional shareholder of Castellum, Inc. is ESSEX INVESTMENT MANAGEMENT CO LLC, holding approximately 2.15 million shares — equal to 2.47% of outstanding shares — as of September 30, 2025.
A total of 42 institutional investors currently hold CTM stock, with a combined institutional value of approximately $9,270,435 as of the most recent 13F filing period.
Frequently asked questions
CTM ownershipCastellum, Inc. (CTM) is primarily owned by institutional investors, who hold approximately 9.0% of shares. The largest shareholder is ESSEX INVESTMENT MANAGEMENT CO LLC with a 2.47% stake. Company insiders hold 21.41%. Data sourced from SEC Form 13F as of September 30, 2025.