Francis Perrin (17.03.1901-27.07.1979) was a French physicist and a member of the Paris Academy of Sciences (1953). He was the son of J. Perrin. He was born in Paris. He graduated from the École Normale (1922) and the University of Paris. In 1923—45 he worked at the University of Paris (professor from 1935, and in 1941 — 44 professor at Columbia University). In 1946 —72 he was professor at the Collège de France, and in 1951—70 he headed the Commissariat for Atomic Energy.
His work concerned molecular physics, optics, and atomic and nuclear physics. He studied Brownian motion, fluorescence, the lifetimes of excited molecules in solutions, and pair production. Independently of V. L. Levshin he developed the theory of polarised luminescence. He was one of the first to conclude that the mass of the neutrino is negligibly small, and in 1939 he calculated the critical mass of uranium for a nuclear fission chain reaction.