MKS Instruments Inc
Ownership
Ownership Structure
Who owns MKS Instruments Inc (MKSI)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 99.4% of the shares are freely tradable; institutional investors hold 104.9%.
Largest Shareholders
Institutions
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| BlackRock Inc | 9.82 | 6,641,730 | +8.2 | 03/31/2026 |
| Amvescap Plc. | 5.50 | 3,721,459 | -3.5 | 03/31/2026 |
| Vanguard Portfolio Management, LLC | 5.45 | 3,685,493 | +0.0 | 03/31/2026 |
| Vanguard Capital Management, LLC | 4.46 | 3,014,201 | +0.0 | 03/31/2026 |
| JPMorgan Chase & Co | 3.10 | 2,096,342 | +35.1 | 03/31/2026 |
| State Street Corp | 3.04 | 2,057,732 | +2.0 | 03/31/2026 |
| FMR Inc | 2.86 | 1,933,843 | -39.5 | 03/31/2026 |
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| American Funds SMALLCAP World A | 3.63 | 2,453,957 | -4.1 | 06/30/2026 |
| iShares Core S&P Mid-Cap ETF | 3.50 | 2,365,286 | +0.0 | 08/31/2026 |
| Vanguard MStar Total Stk Mkt Idx Invest | 3.18 | 2,150,496 | +0.3 | 07/31/2026 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider holdings
| Person | Role | Shares | Value | As of | Type |
|---|---|---|---|---|---|
| Lee John Tseng-Chung | President & CEO | 134,776 | 33,977,097 $ | Aug 14, 2026 | direct |
| Mora Elizabeth | Director | 18,845 | 4,750,913 $ | Sep 1, 2026 | direct |
| Williams John Edward | EVP & GM, PSD | 4,098 | 1,033,066 $ | Aug 3, 2026 | direct |
Holdings as of each person's most recent SEC Form 4 filing — excluding options and RSUs, which are not shares yet. Holdings may have changed between two filings.
Insiders
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| Sep 1, 2026 | Mora Elizabeth | Director | Sell | 300 | 250.96 | 75,288 |
| Aug 14, 2026 | Lee John Tseng-Chung | President & CEO | Sell | 10,000 | 302.01 | 3,020,100 |
| Aug 3, 2026 | Williams John Edward | EVP & GM, PSD | Sell | 457 | 288.31 | 131,758 |
Reportable transactions by officers and major shareholders from SEC Form 4 filings. "Other" includes things like stock grants and option exercises without a buy/sell character. View all insider transactions →
Data as of: September 18, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)
Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.