MAD River Investors is an SEC-registered investment adviser based in Boston, MA that reports managing 2 hedge funds on Form ADV. It reports $403.5 million in regulatory assets under management. Its private funds, of all types, hold $69.7 million in gross assets. Its disclosed U.S. stock holdings returned an estimated +22.3% 2026 YTD through Jun 30 (S&P 500: +9.5%), based on 13F filings. Over a longer period they returned an estimated +67.6% from Q3 2024 to Q2 2026, compared with +37.2% for the S&P 500, based on 13F filings.
- Regulatory assets under management
- $403.5 millionForm ADV Item 5.F
- Gross assets of private funds
- $69.7 millionAll private fund types, Form ADV
- Hedge funds managed
- 22 private funds in total
- Employees
- 6Form ADV Item 5.A
- Registration
- SEC-registered adviserCRD 130585
- Latest Form ADV
- 07/07/2026Disciplinary disclosures: none reported
Estimated 13F portfolio performance
| Quarter | Est. 13F return | S&P 500 |
|---|---|---|
| Q2 2026 | -3.6% | +14.8% |
| Q1 2026 | +26.9% | -4.6% |
| Q4 2025 | -7.0% | +2.4% |
| Q3 2025 | -0.3% | +7.8% |
| Q2 2025 | -5.6% | +10.4% |
| Q1 2025 | +10.0% | -4.5% |
| Q4 2024 | +24.4% | +2.1% |
| Q3 2024 | +14.4% | +5.4% |
Estimate of the firm's disclosed long U.S. stock portfolio from its quarterly 13F filings, holding each quarter-end portfolio to the next quarter-end at prices implied by all 13F filers. It is a price return before dividends and fees, ignores shorts, options, bonds, cash and trading within the quarter, and is not the return of any fund. Disclosures
Largest disclosed holdings
- Texas Pacific Land Corp$124.9 million
- Permian Basin RTY TR$25.2 million
- Landbridge Company LLC$21.2 million
- Hawaiian Elec Industries$17.9 million
- Grayscale Bitcoin Trust ETF$16.4 million
- Miami Intl Hldgs Inc$10.7 million
- Waterbridge Infrastructure L$9.2 million
- Mesabi TR$8.2 million
- Wheaton Precious Metals Corp$6.3 million
- Franco Nev Corp$4.7 million
As of 2026-06-30, from 13F filing by MAD River Investors.
From SEC filings. Firm data comes from the SEC's Form ADV data as of Oct 2, 2026; performance estimates come from Form 13F. HedgeMountain has not verified this information, and it is not an offer, solicitation or recommendation. Full disclosures