Altimeter Capital Management, LP — ARM HOLDINGS PLC ARM: Quarterly 13F Position History
Altimeter Capital Management, LP has reported ARM HOLDINGS PLC (ARM) on 5 13F-HR filings in Pactolio's tracked window, first appearing in Q1 2025. As of Q1 2026, the position is sized at 1,715,440 shares ($259.5M market value, 4.55% of the equity book). Quarter-over-quarter share count change: + 1,715,440 (0.0%) .
- 1,715,440Shares Held (Latest Filing)
- $259.5MReported Market Value (Latest Filing)
- 4.55%Portfolio Weight (% of 13F Equity Book)
- +1,715,440Quarter-over-Quarter Share Change
- +$259.5MQuarter-over-Quarter Value Change
- 1,715,440Peak Reported Shares (Historical)
Quarterly 13F-HR Disclosure History Source: SEC 13F-HR filings, 5 quarter s
| Quarter | Shares | QoQ Share Change | Share Change (%) | Market Value | Weight | Implied Price |
|---|---|---|---|---|---|---|
| Q1 2026 | 1,715,440 | +1,715,440 | — | $259.5M | 4.55% | $151.28 |
| Q4 2025 | 0 | 1,098,139 | -100.0% | $0 | 0.00% | — |
| Q3 2025 | 1,098,139 | +164,931 | +17.7% | $155.4M | 2.05% | $141.49 |
| Q2 2025 | 933,208 | +757,608 | +431.4% | $150.9M | 2.18% | $161.74 |
| Q1 2025 | 175,600 | — | — | $18.8M | 0.38% | $106.79 |
Methodology & FAQ
How This Position History Is Sourced
Each row is one SEC Form 13F-HR filing disclosing this position. Share count, market value, and reported quarter are taken verbatim from the filing; portfolio weight is recomputed against the same filing's total reported equity book. Implied price-per-share is market value divided by shares — a quarter-end mark, not the manager's cost basis. See the full methodology document for the normalization rules.
When did Altimeter Capital Management, LP first disclose a ARM position in 13F-HR filings?
Altimeter Capital Management, LP first reported ARM HOLDINGS PLC (ARM) on its 13F-HR filing for the period ending 2025-03-31 (Q1 2025). The position has appeared on 5 reported quarters within Pactolio's tracked window.
What was Altimeter Capital Management, LP's most recent quarter-over-quarter share-count change in ARM?
Between Q4 2025 and Q1 2026, Altimeter Capital Management, LP added 1,715,440 shares of ARM (0.0%), bringing the total reported position to 1,715,440 shares at a market value of $259.5M.
Does the implied price-per-share represent Altimeter Capital Management, LP's cost basis in ARM?
No. The implied price-per-share column is the 13F-HR reported market value divided by reported share count on the filing date (end of quarter). It is a quarter-end mark, not a cost basis or transaction price. Use it as a sanity check on the value column, not as an indicator of the manager's entry or exit price.