James Harris Simons, commonly known as Jim Simons, was an American mathematician, hedge fund manager, investor, and philanthropist renowned for founding Renaissance Technologies, a pioneering quantitative hedge fund. Born on April 25, 1938, in Cambridge, Massachusetts, to an American Jewish family as the only child of Marcia (née Kantor) and Matthew Simons, he was raised in Brookline, Massachusetts. Simons demonstrated early aptitude for mathematics and earned a BS in mathematics from the Massachusetts Institute of Technology in 1958 and a PhD in mathematics from the University of California, Berkeley in 1961 under Bertram Kostant. His academic career included teaching at MIT and Harvard, cryptanalysis for the Institute for Defense Analyses (IDA) during the Vietnam War—where he was dismissed in 1968 for anti-war activism—and chairing the mathematics department at Stony Brook University, where his work advanced differential geometry, including the Chern-Simons form. A known friend of Richard Perry, Simons transitioned to finance in the 1970s, founding Renaissance Technologies in 1982 on Long Island, New York. The firm's Medallion Fund achieved unprecedented returns averaging around 66% annually before fees through algorithmic trading and mathematical models, amassing Simons a net worth of approximately $31.4 billion at his death, cementing his reputation as the 'Quant King' and one of the most successful hedge fund managers in history. In his later years, Simons focused on philanthropy, co-founding the Simons Foundation in 1994 with his wife Marilyn Hawrys (married 1977; previously married to Barbara Bluestein 1959-1974), which supports research in mathematics, physical sciences, life sciences, and autism via initiatives like SFARI. He also backed Math for America and served on boards including the MIT Corporation and Rockefeller University. Simons received the Oswald Veblen Prize in 1976 for geometry work. He had five children, including Nat. Simons died peacefully on May 10, 2024, in New York City at age 86.