Ross Gunn (May 12, 1897 — October 15, 1966) was an American physicist, a key player in the USA nuclear submarine program, and a principal in the Manhattan Project. The New York Times described Gunn as "one of the true fathers of the nuclear submarine program". For his contributions to the Manhattan Project Gunn received the Navy Distinguished Civilian Service Award on September 4, 1945. The National Academies Press said that he "was one of the most versatile physicists of the early and mid-twentieth century". Gunn was a member of the National Academy of Sciences. He also was a professor of physics at American University, the head of the Mechanics and Electricity Division, superintendent of the Aircraft Electrical Division, and technical director of the Army-Navy Precipitation Static Project, a technical adviser to the naval administration, director of the Weather Bureau's Physical Research Division. Gunn was key in development of liquid thermal diffusion methods for separating of uranium isotopes for the Manhattan project. He was also a fellow of the Institute of Radio Engineers. Gunn held 45 patents.