James Simons is an American mathematician, hedge fund manager, and philanthropist, best known for founding the quantitative investment firm Renaissance Technologies. Born on April 25, 1938, he earned a Ph.D. in mathematics from Berkeley and worked as a codebreaker for the U.S. Navy during the Vietnam War. Simons revolutionized the finance industry by applying mathematical models and algorithms to trading, leading to significant profits for his firm. His success has made him one of the wealthiest individuals in the world, and he is also known for his contributions to mathematics and science through various philanthropic efforts.