Joseph Polchinski is an American theoretical physicist and string theorist. He graduated from Canyon del Oro High School in Tucson, Arizona in 1971, obtained his B.S. degree from Caltech in 1975, and his Ph.D. from the University of California, Berkeley in 1980 under the supervision of Stanley Mandelstam. After postdoctoral positions at SLAC and Harvard he was professor at the University of Texas at Austin from 1984 to 1992. Since 1992 he has been professor at the University of California, Santa Barbara and a permanent member of the Kavli Institute for Theoretical Physics in Santa Barbara.
Polchinski is the author of the two volume textbook, String Theory, published in 1998. Among his contributions to theoretical physics, D-branes are the best known. In 2008 he won the Dirac Medal for his work in superstring theory.