Patrick Maynard Stuart Blackett, Baron Blackett OM CH FRS (18 November 1897 – 13 July 1974) was an English experimental physicist known for his work on cloud chambers, cosmic rays, and paleomagnetism. He also made a major contribution in World War II advising on military strategy and developing Operational Research. His left-wing views saw an outlet in third world development and in influencing policy in the Labour Government of the 1960s.