Klaus Emil Julius Fuchs (December 29, 1911 - January 28, 1988) was a German-British theoretical physicist and atomic spy who in 1950 was convicted of supplying information from the American, British and Canadian atomic bomb research (the Manhattan Project) to the USSR during and shortly after World War II. While at the Los Alamos National Laboratory, Fuchs was responsible for many significant theoretical calculations relating to the first fission weapons and later, the early models of the hydrogen bomb, the first fusion weapon. After Fuchs' confession and a trial lasting less than 90 minutes, he was sentenced to fourteen years' imprisonment, the maximum for espionage and stripped of his British citizenship. He was released in 1959 and promptly emigrated to East Germany. He received the Patriotic Order of Merit, the Order of Karl Marx and the National Prize of East Germany. He died in 1988 at the age of 76.