The Simons Foundation is a leading American private foundation established in 1994 by Jim and Marilyn Simons. Based in New York City, it focuses on advancing research in mathematics and the basic sciences. With assets exceeding $5 billion, it is one of the largest charitable organizations in the U.S. The foundation operates as a nonprofit and is guided by a board of trustees.

The foundation primarily provides grant funding to researchers and projects in four main areas: Mathematics and Physical Sciences, Life Sciences, Autism Research through the Simons Foundation Autism Research Initiative (SFARI), and Outreach, Education, and Engagement in science and culture. It also runs the Flatiron Institute, a multidisciplinary research center that focuses on computational science and hosts several specialized centers for various fields of study. The foundation aims to promote scientific collaboration, diversity of perspectives, and public engagement, significantly impacting research and education in the scientific community.