William Karush (1 March 1917 – 22 February 1997) was an American professor of mathematics at California State University at Northridge and was a mathematician best known for his contribution to Karush–Kuhn–Tucker conditions.

In his master's thesis he was the first to publish these necessary conditions for the inequality-constrained problem,[1] although he became renowned after a seminal conference paper by Harold W. Kuhn and Albert W.

[2] He also worked as a physicist for the Manhattan Project, although he signed the Szilárd petition and became a peace activist afterwards.

[3] Sam and Tillie (formerly Shmuel and Tybel) Karush immigrated to the United States from Bialystok, then under Russian control, now Poland.

He attended the Central YMCA College in Chicago for two years before transferring to University of Chicago, where he received a Bachelor of Science in 1938 and a Masters of Science in 1939.