Marilyn Simons and her family are ranked No. 66 on the Forbes 2026 World’s Billionaires list with a net worth of $32.5 billion. She co-founded the Simons Foundation with her husband, the hedge fund pioneer Jim Simons, who died in May 2024.
Marilyn Hawrys Simons is the widow of James Harris Simons, the mathematician and founder of the quantitative hedge fund Renaissance Technologies. Stony Brook University is her alma mater. She has no stand-alone entry on Wikipedia, so this profile relies largely on the record of her husband’s career and their joint philanthropy.
Net Worth and Rank
- Forbes 2026 list: No. 66, with $32.5 billion, listed as “Marilyn Simons & family”
- Source of wealth: Jim Simons’s fortune; at his death his net worth was estimated at $31.4 billion
Jim Simons and Renaissance
Jim Simons was born on April 25, 1938, and died on May 10, 2024. He studied at MIT and the University of California, Berkeley, and developed the Chern–Simons form in mathematics. His Renaissance Technologies, based in East Setauket, New York, used mathematical models to invest, and he was called “the most successful hedge fund manager of all time”.
The Simons Foundation
- 1994: Marilyn and Jim Simons co-founded the Simons Foundation to support research in mathematics and the basic sciences
- Stony Brook: the foundation is the university’s top benefactor, and in 2023 it gave $500 million, the second-largest donation to a public university in US history
- Autism research: in 2003 the foundation set up the Simons Foundation Autism Research Initiative (SFARI)
- Giving: Jim Simons gave over $4 billion to philanthropic causes
Why It Matters
The Simons family’s wealth rests on Renaissance Technologies, and its foundation is one of the largest private funders of science in the United States.
Net worth figures change daily with share prices. Rankings here follow the Forbes 2026 World’s Billionaires list, with wealth measured on March 1, 2026.
Image: The auditorium of the Simons Foundation in New York (file photo, 2016; Marilyn Simons is not pictured). Photo: Jim.henderson / Wikimedia Commons (CC0)
