Richard S. Stein (August 21, 1925 – June 21, 2021) was an American scientist.
Stein completed undergraduate at Brooklyn Polytechnic, where he performed some of the first studies of the dimensions of polymer molecules in solution using light scattering.
Stein joined the faculty of University of Massachusetts Amherst in 1950 as an assistant professor and initiated its polymer program.
Stein later served as Emeritus Goessmann Professor of Chemistry.
He was elected to membership in the National Academies of Sciences and of Engineering.