Institutional HoldersBeta

Who holds a company, from every 13F filed for the quarter, one row per filer exactly as filed, against the latest share count the company reported.

Terrestrial Energy Inc. /DE/

CIK 0002019804IMSRIMSRW· quarter ending 2026-06-30

Shares outstanding

105,935,254

as of 2026-08-11 · 10-Q cover page, filed 2026-08-11

Held by 13F filers

21,561,958

20.4% of shares outstanding

Holders

110

+22 vs 2026-03-31 · 38 new, 16 exited

Value

$151.4M

shares +15.7% vs prior quarter

Share classes (cover page of the 10-Q filed 2026-08-11, as of 2026-08-11)

Class	Listed	Shares outstanding	Held by 13F filers	% of class	Holders	CUSIP
Common stock	IMSR · NASDAQ	105,935,254	21,561,958	20.4%	110	881454102

Each class is compared with its own share count; classes are not added together. A class that is not exchange-listed cannot be held by 13F filers.

Securities (CUSIPs held in 13F this quarter)

tick to combine

Count	CUSIP	Class (as filers write it)	Holders	Shares held	Class shares	% of class	Value	Options	Mapped via
	881454102	COM SHS	110	21,561,958	105,935,254	20.4%	$151.4M	5 call / 5 put	13DG	holders →
	881454110	*W EXP 10/28/203not common	24	12,270,437	—	—	$43.3M	1 call / 0 put	prefix	holders →

Totals combine the ticked CUSIPs and update as you tick: common-stock classes by default; preferreds, notes, warrants and depositary shares are listed but not counted. "holders →" shows a single CUSIP on its own. Bonds are held as a principal amount, not shares. Options positions are never counted as holdings. 3 further CUSIPs map to this company (mostly bonds) but no 13F filer held them this quarter.

Top holders (110 of 110 · 881454102)

change vs 2026-03-31

#	Filer	Shares	% of class	Value	Change
1	VANGUARD CAPITAL MANAGEMENT LLC	3,414,196	3.22%	$24.2M	+2,110,744 (+161.9%)
2	EXCHANGE TRADED CONCEPTS, LLC	2,160,074	2.04%	$15.3M	+68,913 (+3.3%)
3	UBS Group AG	1,772,173	1.67%	$12.5M	+1,278,596 (+259.0%)
4	HRT FINANCIAL LP	1,125,849	1.06%	$8.0M	NEW
5	BlackRock, Inc.	1,074,524	1.01%	$7.6M	-46,361 (-4.1%)
6	JPMORGAN CHASE & CO	966,797	0.91%	$6.8M	-106,276 (-9.9%)
7	GEODE CAPITAL MANAGEMENT, LLC	693,934	0.66%	$4.9M	+34,546 (+5.2%)
8	LMR Partners LLP	690,702	0.65%	$4.9M	—
9	D. E. Shaw & Co., Inc.	667,968	0.63%	$4.7M	-546,809 (-45.0%)
10	Hudson Bay Capital Management LP	589,293	0.56%	$4.2M	+137,006 (+30.3%)
11	Pacer Advisors, Inc.	574,618	0.54%	$4.1M	NEW
12	SUSQUEHANNA INTERNATIONAL GROUP, LLP	571,832	0.54%	$4.0M	+241,556 (+73.1%)
13	WINTON GROUP Ltd	504,000	0.48%	$3.6M	+7,700 (+1.6%)
14	MORGAN STANLEY	412,815	0.39%	$2.9M	+127,266 (+44.6%)
15	Verition Fund Management LLC	374,958	0.35%	$2.7M	-70,000 (-15.7%)
16	VANGUARD FIDUCIARY TRUST CO	365,772	0.35%	$2.6M	+65,365 (+21.8%)
17	Vennlight Capital Management, LP	353,010	0.33%	$2.5M	-222,489 (-38.7%)
18	STATE STREET CORP	346,696	0.33%	$2.5M	+1,176 (+0.3%)
19	CHARLES SCHWAB INVESTMENT MANAGEMENT INC	333,599	0.31%	$2.4M	-4,392 (-1.3%)
20	HIGHBRIDGE CAPITAL MANAGEMENT LLC	244,000	0.23%	$1.7M	NEW
21	Magnetar Financial LLC	244,000	0.23%	$737K	—
22	JANE STREET GROUP, LLC	240,719	0.23%	$1.7M	NEW
23	Alyeska Investment Group, L.P.	222,000	0.21%	$1.6M	-500,000 (-69.3%)
24	RENAISSANCE TECHNOLOGIES LLC	183,800	0.17%	$1.3M	-224,100 (-54.9%)
25	Creek Drive Management Group LLC	175,000	0.17%	$1.2M	-155,000 (-47.0%)
26	CastleKnight Management LP	165,400	0.16%	$1.2M	+104,700 (+172.5%)
27	FNY Investment Advisers, LLC	151,650	0.14%	$1.1M	+85,490 (+129.2%)
28	Shay Capital LLC	134,539	0.13%	$953K	+16,453 (+13.9%)
29	NORTHERN TRUST CORP	126,539	0.12%	$896K	+2,002 (+1.6%)
30	Yorkville Advisors Global, LP	122,000	0.12%	$864K	—
31	Harraden Circle Investments, LLC	122,000	0.12%	$864K	—
32	Periscope Capital Inc.	122,000	0.12%	$730K	—
33	COMMONWEALTH EQUITY SERVICES, LLC	110,794	0.10%	$784K	+10,663 (+10.6%)
34	TORONTO DOMINION BANK	110,000	0.10%	$779K	-115,974 (-51.3%)
35	MILLENNIUM MANAGEMENT LLC	96,035	0.09%	$680K	NEW
36	XTX Topco Ltd	94,601	0.09%	$670K	NEW
37	Mount Lucas Management LP	93,000	0.09%	$658K	+41,500 (+80.6%)
38	Aquatic Capital Management LLC	88,952	0.08%	$630K	NEW
39	SONA ASSET MANAGEMENT (US) LLC	85,566	0.08%	$606K	—
40	Squarepoint Ops LLC	85,500	0.08%	$605K	-87,709 (-50.6%)
41	VOLORIDGE INVESTMENT MANAGEMENT, LLC	83,374	0.08%	$590K	NEW
42	Engineers Gate Manager LP	82,295	0.08%	$583K	NEW
43	TIEMANN INVESTMENT ADVISORS, LLC	75,995	0.07%	$538K	—
44	MOORE CAPITAL MANAGEMENT, LP	75,000	0.07%	$531K	—
45	IMC-Chicago, LLC	74,991	0.07%	$531K	+53,834 (+254.5%)
46	Parallax Volatility Advisers, L.P.	68,518	0.06%	$485K	NEW
47	AQR CAPITAL MANAGEMENT LLC	59,777	0.06%	$423K	NEW
48	GOLDMAN SACHS GROUP INC	59,425	0.06%	$421K	-336,813 (-85.0%)
49	Swiss National Bank	56,600	0.05%	$401K	—
50	Balyasny Asset Management L.P.	56,461	0.05%	$400K	-149,442 (-72.6%)
51	ALLSTATE CORP	50,205	0.05%	$355K	NEW
52	MMCAP International Inc. SPC	44,279	0.04%	$313K	—
53	LPL Financial LLC	42,381	0.04%	$300K	+15,677 (+58.7%)
54	TUDOR INVESTMENT CORP ET AL	42,225	0.04%	$299K	+30,971 (+275.2%)
55	ExodusPoint Capital Management, LP	40,205	0.04%	$285K	NEW
56	SIMON QUICK ADVISORS, LLC	40,000	0.04%	$283K	—
57	Y-Intercept (Hong Kong) Ltd	38,150	0.04%	$270K	NEW
58	FLAX POND CAPITAL, LLC	37,000	0.03%	$239K	+21,000 (+131.3%)
59	CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM	31,276	0.03%	$221K	—
60	CANADA PENSION PLAN INVESTMENT BOARD	29,000	0.03%	$205K	NEW
61	AMERICAN CENTURY COMPANIES INC	26,768	0.03%	$190K	NEW
62	UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC	26,399	0.02%	$187K	-37,101 (-58.4%)
63	BANK OF AMERICA CORP /DE/	25,431	0.02%	$180K	-107,319 (-80.8%)
64	PRELUDE CAPITAL MANAGEMENT, LLC	25,000	0.02%	$177K	+12,381 (+98.1%)
65	Advisory Services Network, LLC	24,555	0.02%	$174K	+3,620 (+17.3%)
66	DRW Securities, LLC	22,000	0.02%	$156K	—
67	Legal & General Group Plc	21,537	0.02%	$152K	+6,308 (+41.4%)
68	Foundations Investment Advisors, LLC	21,000	0.02%	$149K	NEW
69	SLT Holdings LLC	21,000	0.02%	$149K	NEW
70	MARSHALL WACE, LLP	20,278	0.02%	$144K	-5,999 (-22.8%)
71	Vanguard Global Advisers, LLC	19,963	0.02%	$141K	-7,092 (-26.2%)
72	VANGUARD ASSET MANAGEMENT, Ltd	19,453	0.02%	$138K	—
73	JONES FINANCIAL COMPANIES LLLP	17,382	0.02%	$117K	+8,729 (+100.9%)
74	Zurcher Kantonalbank (Zurich Cantonalbank)	17,093	0.02%	$121K	NEW
75	Bank of New York Mellon Corp	16,911	0.02%	$120K	-124 (-0.7%)
76	BANK OF MONTREAL /CAN/	16,469	0.02%	$117K	+3,949 (+31.5%)
77	Valeo Financial Advisors, LLC	15,000	0.01%	$106K	NEW
78	DNB Asset Management AS	11,430	0.01%	$81K	NEW
79	Vanguard Investments Australia, Ltd.	10,674	0.01%	$76K	—
80	CITADEL ADVISORS LLC	10,061	0.01%	$71K	-1,267,197 (-99.2%)
81	Cornerstone Advisory, LLC	10,003	0.01%	$71K	NEW
82	INSIGNEO ADVISORY SERVICES, LLC	10,000	0.01%	$71K	—
83	FIRST FOUNDATION ADVISORS	10,000	0.01%	$71K	—
84	Rockefeller Capital Management L.P.	7,000	0.01%	$50K	NEW
85	Federation des caisses Desjardins du Quebec	6,450	0.01%	$46K	+1,100 (+20.6%)
86	KLP KAPITALFORVALTNING AS	6,300	0.01%	$45K	—
87	US BANCORP \DE\	4,500	0.00%	$32K	NEW
88	SkyView Investment Advisors, LLC	3,844	0.00%	$27K	NEW
89	ROYAL BANK OF CANADA	3,333	0.00%	$24K	-22,288 (-87.0%)
90	OSAIC HOLDINGS, INC.	2,737	0.00%	$19K	+208 (+8.2%)
91	Anchor Investment Management, LLC	2,100	0.00%	$15K	—
92	NATIONAL BANK OF CANADA /FI/	1,999	0.00%	$14K	-5,501 (-73.3%)
93	CITIGROUP INC	1,510	0.00%	$11K	-25,398 (-94.4%)
94	FMR LLC	1,300	0.00%	$9K	NEW
95	Arax Advisory Partners	903	0.00%	$6K	NEW
96	Cherry Tree Wealth Management, LLC	692	0.00%	$5K	—
97	EverSource Wealth Advisors, LLC	594	0.00%	$4K	NEW
98	Caitong International Asset Management Co., Ltd	447	0.00%	$3K	NEW
99	Essential Partners LLC	407	0.00%	$3K	NEW
100	BARCLAYS PLC	354	0.00%	$3K	NEW
101	Farther Finance Advisors, LLC	301	0.00%	$2K	+53 (+21.4%)
102	Steward Partners Investment Advisory, LLC	200	0.00%	$1K	—
103	Parallel Advisors, LLC	171	0.00%	$1K	NEW
104	Redwood Park Advisors LLC	109	0.00%	$772	+22 (+25.3%)
105	Allworth Financial LP	72	0.00%	$510	NEW
106	SJS Investment Consulting Inc.	59	0.00%	$418	NEW
107	Quarry LP	49	0.00%	$347	NEW
108	HOLLENCREST CAPITAL MANAGEMENT	30	0.00%	$212	NEW
109	ROTHSCHILD INVESTMENT LLC	18	0.00%	$127	NEW
110	Clearstead Advisors, LLC	10	0.00%	$71	NEW

Exited since 2026-03-31 (16 filers; largest 16 shown)

HITE Hedge Asset Management LLC	−240,113
K2 PRINCIPAL FUND, L.P.	−80,000
Massar Capital Management, LP	−65,000
Diametric Capital, LP	−59,191
BLUEFIN CAPITAL MANAGEMENT, LLC	−32,463
Brevan Howard Capital Management LP	−25,153
FLOW TRADERS U.S. LLC	−21,530
Schonfeld Strategic Advisors LLC	−19,254
LEVEL FOUR ADVISORY SERVICES, LLC	−16,375
T3 Companies, LLC	−16,295
WealthPlan Investment Management, LLC	−10,206
DB Fitzpatrick & Co, Inc	−150
Tower Research Capital LLC (TRC)	−103
Signature Resources Capital Management, LLC	−70
Root Financial Partners, LLC	−50
CoreCap Advisors, LLC	−7

Large holders from 13D/13G (latest per reporting person, last 2 years)

Filed when a holder crosses 5% or changes materially, so often more current than the quarter-end 13F. Percentages are the filer's own, against the share count they used.

Reporting person	Form	Filed	Event	Shares	% of class
Citadel Securities LLC	SCHEDULE 13G/A	2026-02-17	2025-12-31	274,588	0.3%
Kenneth Griffin	SCHEDULE 13G/A	2026-02-17	2025-12-31	2,303,796	2.2%
Citadel Advisors Holdings LP	SCHEDULE 13G/A	2026-02-17	2025-12-31	2,029,208	1.9%
Citadel Advisors LLC	SCHEDULE 13G/A	2026-02-17	2025-12-31	2,029,208	1.9%
Citadel GP LLC	SCHEDULE 13G/A	2026-02-17	2025-12-31	2,029,208	1.9%
Citadel Securities GP LLC	SCHEDULE 13G/A	2026-02-17	2025-12-31	274,588	0.3%
Citadel Securities Group LP	SCHEDULE 13G/A	2026-02-17	2025-12-31	274,588	0.3%
Roberto M. Sella 2012 Family Trust	SCHEDULE 13G	2026-01-22	2025-10-29	1,538,319	1.44%
Roberto Marco Sella	SCHEDULE 13G	2026-01-22	2025-10-29	15,378,689	14.34%
LL Charitable Foundation	SCHEDULE 13G	2026-01-22	2025-10-29	653,334	0.62%
Linden Capital L.P.	SCHEDULE 13G/A	2025-11-12	2025-09-30	209,426	0.9%
Linden GP LLC	SCHEDULE 13G/A	2025-11-12	2025-09-30	209,426	0.9%
SUPERNOVA MANAGEMENT LLC	SCHEDULE 13G/A	2025-11-12	2025-09-30	142,304	0.62%
Siu Min Wong	SCHEDULE 13G/A	2025-11-12	2025-09-30	209,426	0.9%
MAGNETAR FINANCIAL LLC	SCHEDULE 13G/A	2025-11-12	2025-09-30	142,304	0.62%
MAGNETAR CAPITAL PARTNERS LP	SCHEDULE 13G/A	2025-11-12	2025-09-30	142,304	0.62%
DAVID J. SNYDERMAN	SCHEDULE 13G/A	2025-11-12	2025-09-30	142,304	0.62%
Linden Advisors LP	SCHEDULE 13G/A	2025-11-12	2025-09-30	209,426	0.9%
David LeBlanc	SCHEDULE 13D	2025-11-04	2025-10-28	11,400,410	9.7%
Simon Irish	SCHEDULE 13D	2025-11-04	2025-10-28	13,586,445	12.8%
LMR Partners (Ireland) Limited	SCHEDULE 13G/A	2025-08-14	2025-06-30	941,287	4.1%
Merus Global Investments, LLC	SCHEDULE 13G/A	2025-08-14	2025-06-30	866,058	3.8%
First Trust Capital Management L.P.	SCHEDULE 13G/A	2025-08-14	2025-06-30	1,071,124	4.66%
LMR Partners AG	SCHEDULE 13G/A	2025-08-14	2025-06-30	941,287	4.1%
LMR PARTNERS (DIFC) Ltd	SCHEDULE 13G/A	2025-08-14	2025-06-30	941,287	4.1%
Ben Levine	SCHEDULE 13G/A	2025-08-14	2025-06-30	941,287	4.1%
LMR Partners LLC	SCHEDULE 13G/A	2025-08-14	2025-06-30	941,287	4.1%
LMR Partners LLP	SCHEDULE 13G/A	2025-08-14	2025-06-30	941,287	4.1%
LMR PARTNERS Ltd	SCHEDULE 13G/A	2025-08-14	2025-06-30	941,287	4.1%
Stefan Renold	SCHEDULE 13G/A	2025-08-14	2025-06-30	941,287	4.1%
FTCS Sub GP LLC	SCHEDULE 13G/A	2025-08-14	2025-06-30	1,071,124	4.66%
First Trust Capital Solutions L.P.	SCHEDULE 13G/A	2025-08-14	2025-06-30	1,071,124	4.66%
First Trust Merger Arbitrage Fund	SCHEDULE 13G/A	2025-08-14	2025-06-30	959,283	4.17%
AQR Capital Management, LLC	SCHEDULE 13G/A	2025-08-13	2025-06-30	1,449	0.01%
AQR Capital Management Holdings, LLC	SCHEDULE 13G/A	2025-08-13	2025-06-30	1,449	0.01%
AQR Arbitrage, LLC	SCHEDULE 13G/A	2025-08-13	2025-06-30	1,449	0.01%
Picton Mahoney Asset Management	SCHEDULE 13G/A	2025-08-06	2025-06-30	942,081	4.1%
GOLDMAN SACHS & CO. LLC	SCHEDULE 13G/A	2025-05-12	2025-03-31	746,447	3.2%
THE GOLDMAN SACHS GROUP, INC.	SCHEDULE 13G/A	2025-05-12	2025-03-31	746,447	3.2%
Barclays PLC	SCHEDULE 13G/A	2025-03-21	2024-12-31	1,420,360	6.17%
Ramya Rao	SCHEDULE 13G	2025-02-07	2024-12-31	1,420,360	6.17%

Source: SEC Form 13F-HR information tables for the quarter ending 2026-06-30 (filed within 45 days of quarter end; amendments applied; values normalised to dollars), the share count from the company's latest 10-K/10-Q XBRL cover page, and Schedule 13D/13G filings. Each row is a legal 13F filer as filed — related entities (e.g. Vanguard's advisers) are not merged. Retail brokerage accounts are not reported on 13F, so the remainder is mostly retail and insiders.