John Forbes Nash, Jr. was an American mathematician. He was born in 1928 in West Virginia and was a pioneer in the study of differential geometry and partial differential equations. He also developed an equilibrium theory known as the Nash Equilibrium (of which the prisoner's dilemma is a well-known example). Nash won the 1994 Nobel Prize in Economics, along with two other individuals, for his development of the mathematical foundations of game theory. Nash died in a car crash in 2015.