MASON CAPITAL MANAGEMENT LLC
CIK
1218735
Location
New York, NY
Portfolio Value
Small
$604,249,529
Diversification
Highly concentrated
Filing Date
Global Rank
#3,424
/ 8,795
▼ 488
· as of Jun 2026
Top Industry
Specialty Industrial Machinery
78.1%
3Y Alpha vs SPY
-40.1%
Period ended 3 months ago
Filed Aug 14, 2026 · 53d
26 quarters · since Mar 2020
Clone Performance
Build a hypothetical price-return history from this filer's public 13F holdings.
View clone backtestPortfolio Concentration
8 tracked positions · as of Jun 30, 2026 · Δ vs Mar 31, 2026Top Position
78.1%
+2.6 pts
Top 5
98.0%
−1.9 pts
Top 10
100.0%
0.0 pts
HHI
6,218
Highly concentrated+267
Portfolio Trend
26 quarters · across all stocks
Sector Breakdown
As of Jun 30, 2026| Sector | % Portfolio | Value |
|---|---|---|
| Industrials | 85.3% | $515,648,993 |
| Healthcare | 6.9% | $41,445,040 |
| Communication Services | 6.6% | $39,595,614 |
| Real Estate | 1.3% | $7,559,882 |
| Unclassified | 0.0% | $0 |
Last Quarter's Activity
Export CSVTrimmed
Positions the filer reduced
1 positions
| Ticker | Company | Δ Shares | Shares | Value | Open |
|---|---|---|---|---|---|
| NVRI | Enviri Corp | −2,723,577 | 1,770,959 | $38,872,550 | |
| No positions match the current search. | |||||
New Positions
Positions the filer opened this quarter
1 positions
| Ticker | Company | Shares | Value | Open |
|---|---|---|---|---|
| GRPN | Groupon, Inc. | 657,144 | $15,810,884 | |
| No positions match the current search. | ||||
Sold Out
Positions the filer fully exitedNo qualifying positions this quarter.
8 tracked positions ·
$604,249,529 total
· filing declares
9 positions · $607,022,468
· as of Jun 30, 2026
| Ticker | Company | Type | Shares | Value (USD) | % of Portfolio | History |
|---|---|---|---|---|---|---|
| ATS |
ATS Corp /ATS
Industrials
|
Held | 16,404,170 | $472,112,012 | 78.13% | |
| BKD |
Brookdale Senior Living Inc.
Healthcare
|
Added | 2,575,826 | $41,445,040 | 6.86% | |
| NVRI |
Enviri Corp
Industrials
|
Reduced | 1,770,959 | $38,872,550 | 6.43% | |
| CCO |
Clear Channel Outdoor Holdings, Inc.
Communication Services
|
Held | 9,828,401 | $23,784,730 | 3.94% | |
| GRPN |
Groupon, Inc.
Communication Services
|
NEW | 657,144 | $15,810,884 | 2.62% | |
| RC |
Ready Capital Corp
Real Estate
|
Held | 4,319,933 | $7,559,882 | 1.25% | |
| JELD |
JELD-WEN Holding, Inc.
Industrials
|
Added | 3,109,621 | $4,664,431 | 0.77% | |
|
|
Held | 400,000 | $0 | 0.00% |
Covers the securities this platform tracks: U.S.-listed common stock and the put/call positions reported on it. A 13F can also report security types outside that coverage — preferred shares, bonds, warrants, untracked share classes — so the filing's own declared total can exceed the figures above. The source filing is linked at the top of this table.