Renaissance Technologies LLC is an American hedge fund firm based in East Setauket, New York, on Long Island, which specializes in systematic trading using quantitative models derived from mathematical and statistical analyses. The company was founded in 1982 by James Simons, an award-winning mathematician and former Cold War code breaker.

In 1988, the firm established its most profitable portfolio, the Medallion Fund, which used an improved and expanded form of Leonard Baum's mathematical models, improved by algebraist James Ax, to explore correlations from which they could profit. Simons and Ax started a hedge fund and named it Medallion in honor of the math awards that they had won.