James “Jim” Simons, a renowned mathematician and pioneering investor who built a fortune on Wall Street and then became one of the nation’s biggest philanthropists, has died at age 86.

The charitable foundation that Simons co-founded with his wife, Marilyn, announced that Simons died Friday in New York. No cause of death was given.

“Jim was an exceptional leader who did transformative work in mathematics and developed a world-leading investment company,” Simons Foundation President David Spergel said in a post on the foundation’s website. “Together with Marilyn Simons, the current Simons Foundation board chair, Jim created an organization that has already had enormous impact in mathematics, basic science and our understanding of autism.”

Simons’ first career was in mathematics, for which he won acclaim. But in 1978, he traded academia for Wall Street. The hedge fund he created, which eventually became known as Renaissance Technologies, pioneered the use of mathematical modeling — also known as quantitative trading — to pick stocks and other investments. The approach was wildly successful, helping Simons and his wife build over the years an estimated net worth of more than $30 billion.

James Harris Simons was born in Newton, Massachusetts. He showed an affinity for math and numbers early on and went on to earn an undergraduate degree in mathematics from the Massachusetts Institute of Technology in 1958 and a doctorate in math from the University of California, Berkeley, in 1961.

Simons spent some time teaching at MIT and Harvard University before taking a job at the Institute for Defense Analyses in Princeton, New Jersey, as a code breaker for the National Security Agency. And from 1968 to 1978, he was chairman of the mathematics department at the State University of New York at Stony Brook.

In 1976, Simons received the American Mathematical Society’s Oswald Veblen Prize in Geometry for research that would prove to be influential to string theory and other areas of physics.

In 1978, a year after getting married, Simons started his investment firm. He retired as CEO of the hedge fund in 2010, then focused on philanthropic work through the foundation he and his wife founded in 1994 to support scientists and organizations engaged in research in science, math and education.

Over the years, the couple donated billions of dollars to hundreds of philanthropic causes.

In 2023, they gave $500 million through their foundation to the State University of New York at Stony Brook to support the university’s endowment and boost scholarships, professorships, research and clinical care.

Simons came in second behind only Warren Buffett in the Chronicle of Philanthropy’s list of the biggest charitable donations from individuals or their foundations in 2023.

He is survived by his wife, three children, five grandchildren, and a great-grandchild.