Gregory Breit was born on July 14, 1899 in Nickolaev, Russia. He attended the School of Emperor Alexander from 1909 to 1915. He immigrated to the United States with his family in 1915 and became a naturalized citizen in 1918. Breit received the A.B. (1918), the M.A. (1920), and the Ph.D. (1921) from Johns Hopkins University. He was a National Research Council Fellow at the University of Leyden from 1921 to 1922, and at Harvard University from 1922 to 1923. He was an assistant professor of physics at the University of Minnesota (1923-1924), professor of physics at New York University (1929-1934), and Yale University (1947-1968), and a Distinguished Service Professor of physics at the State University of New York at Buffalo (1968-1976). He conducted research at the Carnegie Institution in Washington, D.C., the Institute for Advanced Study at Princeton University, the Applied Physics Laboratory at Johns Hopkins University, the Ballistic Research Laboratory at Aberdeen Proving Ground, Maryland, the Naval Ordnance Laboratory, and at the University of Chicago, where as the coordinator of the Fast Neutron Project, Metallurgical Laboratory (Manhattan Project), he was involved in the early development of the atom bomb. Breit was the recipient of the National Medal of Science, the Franklin Medal, and the T. W. Bonner Prize of the American Physical Society. He died in Salem, Oregon in 1981.