John Crank (6 February 1916 – 3 October 2006) was a mathematical physicist, best known for his work on the numerical solution of partial differential equations.

Crank studied at Manchester University from 1934 to 1938, where he was awarded a BSc and MSc as a student of Lawrence Bragg and Douglas Hartree.

He worked on ballistics during the Second World War, and was then a mathematical physicist at Courtaulds Fundamental Research Laboratory from 1945 to 1957.

He served two terms of office as vice-principal of Brunel before his retirement in 1981, when he was granted the title of professor emeritus.

He is best known for his work with Phyllis Nicolson on the heat equation, which resulted in the Crank–Nicolson method.