Renaissance Technologies LLC, also known as RenTech or RenTec, is an American hedge fund based in East Setauket, New York, on Long Island, which specializes in systematic trading using quantitative models derived from mathematical and statistical analysis. Their signature Medallion fund is famed for the best record in investing history. Renaissance was founded in 1982 by James Simons, a mathematician who formerly worked as a code breaker during the Cold War.

A hedge fund is a pooled investment fund that holds liquid assets and that makes use of complex trading and risk management techniques to improve investment performance and insulate returns from market risk. Among these portfolio techniques are short selling and the use of leverage and derivative instruments. In the United States, financial regulations require that hedge funds be marketed only to institutional investors and high-net-worth individuals.