Karl Cooper Rubin (born January 27, 1956) is an American mathematician at University of California, Irvine as Thorp Professor of Mathematics.

Between 1997 and 2006, he was a professor at Stanford, and before that worked at Ohio State University between 1987 and 1999.

He was the first mathematician (1986) to show that some elliptic curves over the rationals have finite Tate–Shafarevich groups.

[1] Rubin graduated from Princeton University in 1976, and obtained his Ph.D. from Harvard in 1981.

[4] In 1988, Rubin received a National Science Foundation Presidential Young Investigator award, and in 1992 won the American Mathematical Society Cole Prize in number theory.