William Drexel Duke (born 1958) is an American mathematician specializing in number theory. Duke studied at the University of New Mexico and then at New York University (Courant Institute), from which he received his Ph.D. in 1986 under the direction of Peter Sarnak. After a postdoctoral stint at the University of California, San Diego he joined the faculty of Rutgers University, where he stayed until becoming a Professor of Mathematics at the University of California, Los Angeles. Since 2015 he has been Chair of the mathematics department at UCLA.