Joseph Polchinski (May 16, 1954 – February 2, 2018) was an American theoretical physicist and string theorist. He was born in White Plains, New York. Polchinski wrote the two-volume textbook "String Theory", published in 1998. Among his many contributions to theoretical physics, D-branes are the best known. In 2008 he won the Dirac Medal for his work in superstring theory. He won the 2017 Fundamental Physics Prize.