American physicist for whom the Franck–Condon principle was named and who applied quantum mechanics to an understanding of the atom and its nucleus.

During World War II Condon made valuable contributions to the development of both atomic energy and radar. In 1943 he helped J. Robert Oppenheimer recruit the group that made the first atomic bombs at Los Alamos, N.M. In 1946 he was a consultant to the committee of the Senate that drafted the legislation that created the Atomic Energy Commission; in the aftermath of the struggle to put atomic energy under civilian control he was attacked by the House Committee on Un-American Activities, one of the strongest opponents of civilian control. Condon was director of the National Bureau of Standards (1945–51) and president of both the American Physical Society (1946) and the American Association for the Advancement of Science (1953). In 1966 the Air Force Office of Scientific Research appointed him director of a project to investigate flying saucers (unidentified flying object), from which grew the Condon report, The Scientific Study of Unidentified Flying Objects (1969).