Quantum-Si incorporated (QSI) Ownership
QSI ownership summary
as of October 18, 2026- Institutions
- 24.8% of shares outstanding
- Insiders
- 10.45% of shares outstanding
- Shares outstanding
- 198.9M
- Float
- 180.2M shares available to trade
- Short interest
- 6.63% 11.8M shares short
- Days to cover
- 3.88 short interest down 9.3% vs prior month
- Institutions 24.77%
- Insiders 10.45%
- Other investors 64.78%
QSI top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Vanguard Capital Management, LLC | 3.46% | 7.6M | $8.5M | +556,301 (+7.9%) | June 30, 2026 |
| 2 | ARK Investment Management LLC | 3.27% | 7.2M | $8.0M | +288,839 (+4.2%) | June 30, 2026 |
| 3 | BlackRock Inc | 2.39% | 5.2M | $5.9M | −8.2M (−61.0%) | June 30, 2026 |
| 4 | Amova Asset Management Americas, Inc | 1.77% | 3.9M | $4.4M | −506,436 (−11.5%) | June 30, 2026 |
| 5 | Sumitomo Mitsui Trust Group Inc | 1.77% | 3.9M | $4.4M | −506,436 (−11.5%) | June 30, 2026 |
| 6 | Millennium Management LLC | 1.43% | 3.1M | $3.5M | +3.1M (0.0%) | June 30, 2026 |
| 7 | UBS Group AG | 1.17% | 2.6M | $2.9M | +859,370 (+50.5%) | June 30, 2026 |
| 8 | AQR Capital Management LLC | 1.07% | 2.3M | $2.6M | −43,514 (−1.8%) | June 30, 2026 |
| 9 | Geode Capital Management, LLC | 1.02% | 2.2M | $2.5M | −1.6M (−41.7%) | June 30, 2026 |
| 10 | Jane Street Group LLC | 0.98% | 2.1M | $2.4M | +2.1M (0.0%) | June 30, 2026 |
| 11 | Susquehanna International Group, LLP | 0.51% | 1.1M | $1.3M | −347,818 (−23.7%) | June 30, 2026 |
| 12 | Vanguard Fiduciary Trust Co | 0.51% | 1.1M | $1.3M | −569 (−0.1%) | June 30, 2026 |
| 13 | State Street Corp | 0.41% | 891K | $997,630 | −2.9M (−76.4%) | June 30, 2026 |
| 14 | Fosun International Ltd | 0.34% | 744K | $833,207 | — | June 30, 2026 |
| 15 | Renaissance Technologies Corp | 0.25% | 554K | $620,336 | +435,971 (+369.8%) | June 30, 2026 |
| 16 | Vanguard Portfolio Management, LLC | 0.23% | 497K | $556,750 | −1.0M (−67.3%) | June 30, 2026 |
| 17 | The Goldman Sachs Group Inc | 0.22% | 476K | $533,443 | +32,111 (+7.2%) | June 30, 2026 |
| 18 | Northern Trust Corp | 0.21% | 451K | $504,595 | −810,170 (−64.3%) | June 30, 2026 |
| 19 | Amvescap Plc. | 0.20% | 444K | $497,200 | +37,239 (+9.2%) | June 30, 2026 |
| 20 | BNP Paribas Arbitrage, SA | 0.18% | 399K | $446,430 | +360,208 (+938.3%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 9 holders added 7.8M shares and 10 cut 15.9M.
QSI top mutual fund and ETF holders
19 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | ARK Genomic Revolution ETF | 3.13% | 6.9M | $7.7M | +16,754 (+0.2%) | September 30, 2026 |
| 2 | Vanguard MStar Total Stk Mkt Idx Invest | 2.45% | 5.4M | $6.0M | — | August 31, 2026 |
| 3 | Amova ARK Pstv Chg Innovt P JPY Acc | 1.39% | 3.0M | $3.4M | −157,311 (−4.9%) | August 31, 2026 |
| 4 | iShares Biotechnology ETF | 0.60% | 1.3M | $1.5M | −10,024 (−0.8%) | September 30, 2026 |
| 5 | Fidelity Extended Market Index | 0.54% | 1.2M | $1.3M | −60,047 (−4.9%) | August 31, 2026 |
| 6 | Vanguard Health Care ETF | 0.23% | 503K | $563,575 | +2,220 (+0.4%) | August 31, 2026 |
| 7 | iShares Core S&P Total US Stock Mkt ETF | 0.20% | 435K | $486,786 | +380 (+0.1%) | September 30, 2026 |
| 8 | Invesco RAFI US 1500 Small-Mid ETF | 0.19% | 426K | $477,222 | — | September 30, 2026 |
| 9 | ARK Genomic Revolution ETF A USD Acc | 0.18% | 387K | $433,260 | — | September 30, 2026 |
| 10 | Fidelity Total Market Index | 0.15% | 328K | $367,279 | — | August 31, 2026 |
| 11 | Fidelity Series Total Market Index | 0.12% | 271K | $303,057 | — | August 31, 2026 |
| 12 | EA Bridgeway Ultra-Small Company Mkt ETF | 0.09% | 197K | $220,978 | — | September 30, 2026 |
| 13 | iShares Nasdaq US Biotech ETF USD Acc | 0.07% | 148K | $165,338 | +1,284 (+0.9%) | September 30, 2026 |
| 14 | Fidelity ZERO Total Market Index | 0.05% | 106K | $118,907 | — | August 31, 2026 |
| 15 | Fidelity ZERO Extended Market Index | 0.05% | 103K | $114,943 | +40,227 (+64.5%) | August 31, 2026 |
| 16 | Vanguard U.S. Eq Idx £ Acc | 0.04% | 85K | $94,928 | — | August 31, 2026 |
| 17 | Vanguard Balanced Index Inv | 0.04% | 84K | $93,586 | — | August 31, 2026 |
| 18 | Schwab Total Stock Market Index | 0.04% | 77K | $85,842 | — | August 31, 2026 |
| 19 | Goldman Sachs Absolute Ret Trckr Instl | 0.03% | 59K | $65,564 | +4,207 (+7.7%) | June 30, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
QSI insider transactions
latest 20| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2026-04-21 | Jeffry R Keyes | Sell | $0.99 | 37,381 | $37,007 |
| 2026-04-20 | Jeffrey Alan Hawkins | Sell | $1.01 | 83,712 | $84,549 |
| 2026-04-20 | Jeffry R Keyes | Sell | $1.01 | 37,382 | $37,756 |
| 2026-03-23 | Jeffrey Alan Hawkins | Sell | $0.83 | 12,149 | $10,084 |
| 2026-03-23 | Jeffry R Keyes | Sell | $0.83 | 4,422 | $3,670 |
| 2026-03-23 | John S Vieceli | Sell | $0.83 | 11,239 | $9,328 |
| 2026-03-20 | Jeffrey Alan Hawkins | Sell | $0.85 | 11,628 | $9,884 |
| 2026-03-20 | Jeffry R Keyes | Sell | $0.85 | 4,233 | $3,598 |
| 2026-03-20 | John S Vieceli | Sell | $0.85 | 10,758 | $9,144 |
| 2026-03-05 | Charles R Kummeth | Buy | $0.92 | 500,000 | $460,000 |
| 2026-03-05 | Paula Dowdy | Buy | $0.95 | 109,890 | $104,396 |
| 2025-12-22 | Jeffrey Alan Hawkins | Sell | $1.28 | 23,707 | $30,345 |
| 2025-12-22 | John S Vieceli | Sell | $1.28 | 21,927 | $28,067 |
| 2025-12-22 | Jeffry R Keyes | Sell | $1.28 | 8,627 | $11,043 |
| 2025-10-16 | Jonathan M Rothberg | Sell | $3.07 | 26,095 | $80,112 |
| 2025-09-22 | Jeffrey Alan Hawkins | Sell | $1.68 | 10,643 | $17,880 |
| 2025-09-22 | Jeffry R Keyes | Sell | $1.68 | 3,873 | $6,507 |
| 2025-09-22 | John S Vieceli | Sell | $1.68 | 9,843 | $16,536 |
| 2025-09-22 | Todd C Bennett | Sell | $1.68 | 18,482 | $31,050 |
| 2025-06-23 | Jeffrey Alan Hawkins | Sell | $1.61 | 23,705 | $38,165 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
QSI shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns QSI
Institutional investors own 24.8% of Quantum-Si incorporated's shares and insiders 10.45%. The largest holder is Vanguard Capital Management, LLC with 3.46% of the shares (7.6M), as of June 30, 2026. Among the top 20 institutions, 9 added shares and 10 reduced their stake in the latest filings. Short interest is 6.63% of the float, or 3.88 days of average trading volume. The share count rose 3,855.3% since 2019.
Related: QSI analyst forecast, QSI key metrics. See the QSI stock overview for the latest quote and news.
QSI ownership FAQ
Who owns the most Quantum-Si incorporated stock?
The largest shareholders of Quantum-Si incorporated are Vanguard Capital Management, LLC (3.46%), ARK Investment Management LLC (3.27%), BlackRock Inc (2.39%), Amova Asset Management Americas, Inc (1.77%), Sumitomo Mitsui Trust Group Inc (1.77%).
What percentage of Quantum-Si incorporated is owned by institutions?
Institutions hold 24.8% of Quantum-Si incorporated's shares outstanding; insiders hold 10.45%.
Which funds own Quantum-Si incorporated?
The largest fund holders of Quantum-Si incorporated are ARK Genomic Revolution ETF (3.13%), Vanguard MStar Total Stk Mkt Idx Invest (2.45%), Amova ARK Pstv Chg Innovt P JPY Acc (1.39%), iShares Biotechnology ETF (0.60%), Fidelity Extended Market Index (0.54%).
What is Quantum-Si incorporated's short interest?
11.8M shares of Quantum-Si incorporated were sold short, 6.63% of the float; at the average daily volume it would take 3.88 days to cover.
Are insiders buying or selling Quantum-Si incorporated?
Of the latest 20 reported insider transactions in Quantum-Si incorporated (since June 23, 2025), 2 were purchases and 18 were sales.
How many shares of Quantum-Si incorporated are outstanding?
Quantum-Si incorporated has 198.9M shares outstanding, of which 180.2M are in the public float.