Richard Kenneth Guy (30 September 1916 – 9 March 2020) was a British-Canadian mathematician. He was professor emeritus in the Department of Mathematics at the University of Calgary.
Guy was known for his work in number theory, geometry, recreational mathematics, combinatorics, and graph theory. He is best known for co-authorship (with John Conway and Elwyn Berlekamp) of Winning Ways for your Mathematical Plays and authorship of Unsolved Problems in Number Theory.
He also published over 300 papers.