JANA Partners

Barry Rosenstein

Barry Rosenstein founded JANA Partners, an activist investment firm focused on catalysts such as strategic reviews, sales and board refreshment. JANA often works alongside experienced executives it nominates to boards.

SEC filings, CIK 0001998597

Latest public rank: —
13F portfolio value: $1.9B
13F positions: 10
Recent 13D / Form 4: 0

Rank history

Rank in each edition. Locked editions hide their top 5 until they unlock.

Disclosed moves in public editions

The most recent moves from editions free readers can see, newest first.

No moves in a public edition yet.

Top 13F holdings

13F for Q2 2026, filed Aug 14, 2026 (holdings as of Jun 30, 2026). Total reported value $1,902,301,416 across 10 positions.

The latest 13F filed by Sep 30, 2026; newer 13Fs appear as each edition unlocks.

View the 13F on EDGAR ↗

Mercury Sys Inc
MRCY
$484,285,99825.5% of portfolio3,958,849 shtrimmed
Cooper Cos Inc
COO
$256,899,64113.5% of portfolio3,582,480 shadded
Lamb Weston Hldgs Inc
LW
$232,940,33912.3% of portfolio5,394,635 shadded
Fiserv Inc
FISV
$179,625,0249.4% of portfolio3,662,080 shtrimmed
Markel Group Inc
MKL
$149,879,8467.9% of portfolio76,743 shadded
Alkami Technology Inc
ALKT
$122,268,4516.4% of portfolio6,747,707 shadded
Six Flags Entertainment Corp
FUN
$87,672,9094.6% of portfolio4,116,099 shunchanged
Everpure Inc
P
$77,938,7534.1% of portfolio989,196 shnew
Rapid7 Inc
RPD
$54,674,4822.9% of portfolio6,749,936 shadded

Barry Rosenstein: top 13F holdings
Company	Symbol	Shares	Value	% of portfolio	vs. prior 13F
Mercury Sys Inc	MRCY	3,958,849	$484,285,998	25.5%	trimmed
Cooper Cos Inc	COO	3,582,480	$256,899,641	13.5%	added
Lamb Weston Hldgs Inc	LW	5,394,635	$232,940,339	12.3%	added
Fiserv Inc	FISV	3,662,080	$179,625,024	9.4%	trimmed
Markel Group Inc	MKL	76,743	$149,879,846	7.9%	added
Alkami Technology Inc	ALKT	6,747,707	$122,268,451	6.4%	added
Six Flags Entertainment Corp	FUN	4,116,099	$87,672,909	4.6%	unchanged
Everpure Inc	P	989,196	$77,938,753	4.1%	new
Rapid7 Inc	RPD	6,749,936	$54,674,482	2.9%	added

Recent filings

Schedule 13D, 13D/A and Form 4 filings, newest first. Filings through Sep 30, 2026; newer filings appear as each edition unlocks.

No recent Schedule 13D or Form 4 filings through Sep 30, 2026.

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