Irwin Kra (born January 5, 1937) is an American mathematician, who works on the function theory in complex analysis.

Kra studied at Polytechnic Institute of Brooklyn (bachelor's degree in 1960) and at Columbia University, where he graduated in 1964 and received his doctorate in 1966 under supervision of Lipman Bers (Conformal Structure and Algebraic Structure).

Moore instructor at Massachusetts Institute of Technology and then at the State University of New York at Stony Brook, where he chaired from 1975 to 1981 the Faculty of Mathematics.

From 2004 to 2008 he was Director of Math for America, a private organization that is dedicated to the improvement of college education in mathematics in the United States.

With Bernard Maskit in 1998, he published the collected works of Lipman Bers on function theory.