Walter Volodymyr Petryshyn (Vladimir Petryshin) (born 22 January 1929 in Liashky Murovani, Lviv) is a famous Ukrainian mathematician.
He had commenced his studies in Lviv during World War II, but he became a displaced person at the end of the war and continued his schooling in Germany. In 1950 he emigrated from Germany to the United States and completed his education there, living in Paterson, New Jersey. He studied at Columbia University and was awarded a B.A. in 1953, an M.S. in 1954, and a Ph.D. in 1961. Petryshyn's main achievements are in functional analysis. His major results include the development of the theory of iterative and projective methods for the constructive solution of linear and nonlinear abstract and differential equations.
On May 6, 1996 Petryshyn murdered his wife, Ukrainian-American painter Arcadia Olenska-Petryshyn.
In 2012 he became a fellow of the American Mathematical Society.