Alexander (Lex) Schrijver (born 4 May 1948 in Amsterdam) is a Dutch mathematician and computer scientist, a professor of discrete mathematics and optimization at the University of Amsterdam and a fellow at the Centrum Wiskunde & Informatica in Amsterdam. Since 1993 he has been co-editor in chief of the journal Combinatorica.
Schrijver earned his Ph.D. in 1977 from the Vrije Universiteit in Amsterdam, under the supervision of Pieter Cornelis Baayen. He worked for the Centrum Wiskunde & Informatica (under its former name as the Mathematisch Centrum) in pure mathematics from 1973 to 1979, and was a professor at Tilburg University from 1983 to 1989. In 1989 he rejoined the Centrum Wiskunde & Informatica, and in 1990 he also became a professor at the University of Amsterdam. In 2005, he stepped down from management at CWI and instead became a CWI Fellow.
Schrijver was one of the winners of the Delbert Ray Fulkerson Prize of the American Mathematical Society in 1982 for his work with Martin Grötschel and László Lovász on applications of the ellipsoid method to combinatorial optimization; he won the same prize in 2003 for his research on minimization of submodular functions. He won the INFORMS Frederick W. Lanchester Prize in 1986 for his book Theory of Linear and Integer Programming, and again in 2004 for his book Combinatorial Optimization: Polyhedra and Efficiency. In 2003, he won the George B. Dantzig Prize of the Mathematical Programming Society and SIAM for "deep and fundamental research contributions to discrete optimization". In 2006, he was a joint winner of the INFORMS John von Neumann Theory Prize with Grötschel and Lovász for their work in combinatorial optimization, and in particular for their joint work in the book Geometric Algorithms and Combinatorial Optimization showing the polynomial-time equivalence of separation and optimization. In 2008, his work with Adri Steenbeek on scheduling the Dutch train system was honored with INFORMS' Franz Edelman Award for Achievement in Operations Research and the Management Sciences. He won the SIGMA prize of the Dutch SURF foundation in 2008, for a mathematics education project.