Roger Arthur Cowley, FRS, FRSE, FInstPhys (born 24 February 1939) is an English physicist who has specialised in the excitations of solids. He obtained a B.A. in physics from Trinity Hall, University of Cambridge in 1960 and a Ph.D. in 1963. He was appointed professor of physics at the University of Edinburgh in 1970 and professor of experimental philosophy at University of Oxford in 1988.
Cowley made his name in the field of neutron scattering. This work lead to the study of phase transitions.
He was elected Fellow of the Royal Society in 1978.