Mark Massey's AltaRock Partners holds 4.82M shares of Amazon.com Inc (AMZN) worth about $1.2B as of September 30, 2026, according to the 13F-HR filed with the SEC on November 13, 2026. The position is 28.53% of the reported portfolio, the 2nd largest of 8 stock positions. Mark Massey trimmed the share count by 16% in 2026 Q3.
What did the 2026 Q3 filing report for AMZN?
As of September 30, 2026, from the 13F-HR filed November 13, 2026.
| Value | |
|---|---|
| Portfolio weight | 28.53% |
| Shares | 4.82M |
| Reported value | $1.2B |
| Rank in portfolio | 2nd of 8 |
| Largest holding | MSFT at 32.15% |
| Top three holdings | 82.35% of the book |
| Change this quarter | -16% shares |
How concentrated is Mark Massey in AMZN?
AMZN at 28.53% is 2.3 times the average stock position in the Mark Massey portfolio, which is 13%. The largest holding is MSFT at 32.15%. The three largest stocks together are 82.35% of the reported book. A quarter earlier AMZN was 32.21% of the book.
Where does AMZN sit in the Mark Massey portfolio?
AMZN ranks 2nd of 8 stock positions in the Mark Massey portfolio at 28.53%, above the fund's average stock position of 13%. The AMZN cut was the largest of the quarter's 7 position changes by percent change to portfolio. Across the 2026 Q3 portfolio, Mark Massey reported 8 stock positions, with no position opened or closed. The total portfolio value is about $4.21B, down 1% from the prior quarter.
How long has Mark Massey held AMZN?
Mark Massey first reported AMZN in the quarter ended March 31, 2022. The weight peaked at 38.2% in 2026 Q1. Last quarter the fund cut the position by 24%. Every reported trade is on the Mark Massey AMZN trade history page.
Did other funds buy or sell AMZN in 2026 Q3?
Among the other tracked funds that had filed for 2026 Q3 as of November 13, 2026, 16 hold AMZN. Of those, 2 opened it this quarter. The largest buyers of AMZN this quarter were John Armitage, Parnassus Endeavor Fund and Harry Burn. The largest sellers were Lewis Sanders, Polen Capital Management and Nathaniel Simons. Every tracked holder of AMZN is on the AMZN ownership page.
FAQ
What share of the Mark Massey portfolio is AMZN?
AMZN is 28.53% of the Mark Massey portfolio as of 2026 Q3, the 2nd largest of 8 stock positions.
What is the AMZN stake of Mark Massey worth?
Mark Massey holds 4.82M shares of AMZN, worth about $1.2B at September 30, 2026 prices, 28.53% of the reported portfolio.
What are the largest holdings of Mark Massey?
The largest stock positions of Mark Massey as of 2026 Q3 are MSFT (32.15%), AMZN (28.53%) and TDG (21.67%), together 82.35% of the book.
Did Mark Massey's AltaRock Partners change its AMZN position in 2026 Q3?
Mark Massey trimmed the share count by 16% in 2026 Q3.