Emil Julius Klaus Fuchs (29 December 1911 – 28 January 1988) was a German-born British theoretical physicist and atomic spy who in 1950 was convicted of supplying information from the American, British, and Canadian Manhattan Project to the Soviet Union during and shortly after the Second World War. While at the Los Alamos National Laboratory, Fuchs was responsible for many significant theoretical calculations relating to the first nuclear weapons and later the early models of the hydrogen bomb.