William Prager

William Prager (May 23, 1903 in Karlsruhe – March 16, 1980 in Zurich) was a German-born US applied mathematician. In the field of mechanics he is well known for the Drucker–Prager yield criterion.

He was a lecturer at Darmstadt, a deputy director at University of Göttingen, professor at Karlsruhe, University of Istanbul, the University of California, San Diego and Brown University, where he advised Bernard Budiansky. Prager was also on a sabbatical at IBM's research lab in Zurich.

The Society of Engineering Science has awarded the William Prager Medal in Solid Mechanics since 1983 in his honor.