Peter David Lax is a Hungarian-born American mathematician working in the areas of pure and applied mathematics. He was born on May 1, 1926 in Budapest, Hungary. Before being able to complete his studies, Lax was drafted into the U.S. Army. After basic training, the Army sent him to Texas A&M University for more studies, then Oak Ridge National Laboratory, and soon afterwards to the Manhattan Project at Los Alamos, New Mexico. At Los Alamos, he began working as a calculator operator, but eventually moved on to higher-level mathematics. After the war ended, he remained with the Army at Los Alamos for another year, while taking courses at the University of New Mexico, then studied at Stanford University for a semester with Gabor Szego and George Polya. In a 1958 paper Lax stated a conjecture about matrix representations for third order hyperbolic polynomials which remained unproven for over four decades. Interest in the "Lax conjecture" grew as mathematicians working in several different areas recognized the importance of its implications in their field, until it was finally proven to be true in 2003. Lax holds a faculty position in the Department of Mathematics, Courant Institute of Mathematical Sciences, New York University.

Lax has previously received many honors and awards for his work, including the Chauvenet Prize in 1974, the Norbert Wiener Prize of the American Mathematical Society and the Society for Industrial and Applied Mathematics in 1975, the National Medal of Science in 1986, the Wolf Prize in 1987, and shared the American Mathematical Society's Steele Prize in 1992. In 1996, Lax was elected a member of the American Philosophical Society. Lax is also the author of textbooks on functional analysis, linear algebra, calculus, and partial differential equations.