Marilyn Simons inherited a fortune built by her late husband Jim Simons through Renaissance Technologies and has spent decades directing major scientific philanthropy through the Simons Foundation. [1][2]
The investment fortune she inherited
Forbes identifies Marilyn Simons as the widow of Jim Simons, the mathematician and quantitative-investing pioneer who founded Renaissance Technologies. The Simons Foundation likewise describes Jim as the founder of the hedge fund that pioneered quantitative trading. [1][2]
Jim Simons died in May 2024. Marilyn's current billionaire wealth therefore reflects the family fortune created through his investment career rather than a claim that she founded or managed Renaissance Technologies herself. [1][2]
Building a major philanthropic institution
Marilyn and Jim Simons founded the Simons Foundation in 1994. The foundation says Marilyn led it as president until 2021 and now serves as chair of its board, continuing to direct a large philanthropic program focused on mathematics, basic science and education. [2][3]
Her long operating role at the foundation is distinct from the origin of the investment fortune. It documents substantial stewardship of family capital after wealth was created, while Forbes and the foundation history still place the underlying fortune principally in Jim Simons's quantitative-investing career and the assets that passed to the family. [1][2][3]
Sources for background
Sources reviewed Sep 15, 2026.
- Marilyn Simons & family · Forbes · Mar 10, 2026
- Our History · Simons Foundation
- Leadership · Simons Foundation
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