Which American billionaire founded the hedge fund Renaissance Technologies?

James Simons founded the hedge fund that became Renaissance Technologies.

A mathematician by training, Simons moved from academia and government code-breaking into finance. In 1978, he established Monemetrics, an investment company that later evolved into Renaissance Technologies. The firm became famous for applying mathematical models, statistics and computer-driven trading to markets rather than relying mainly on traditional stock-picking judgments.

Simons recruited scientists and mathematicians, including researchers with backgrounds in physics and cryptography. Renaissance’s secretive Medallion Fund became legendary for its extraordinary long-term performance, although it was generally restricted to the firm’s employees and owners. Simons remained a leading figure at Renaissance before retiring as its chief executive in 2010.

The usual confusion is with Ken Griffin, George Soros or Ray Dalio, all major hedge-fund figures but founders of different firms. Simons was also a celebrated geometer and philanthropist. With his wife, Marilyn, he co-founded the Simons Foundation, which supports mathematics and basic scientific research. He died in 2024, but Renaissance remains his defining business creation.