Lyman Parratt (1908-1995) was an American physicist.
Parratt was born in Salt Lake City. He studied at the University of Utah and earned a Ph.D. from the University of Chicago before going on to teach at Cornell University. His time there was interrupted by the outbreak of World War II, when the Navy requested that he work at the Naval Ordnance Laboratory in Washington, D.C., on submarine detection research. Parratt was then recruited to work on the Manhattan Project at Los Alamos, where he was a group leader. After the war, Parratt returned to Cornell. He was well known in his field for his research on X-rays.
Lyman Parratt died on June 29, 1995, in Redmond, Oregon.