John Horton Conway (born December 26, 1937, Liverpool, England) is a prolific mathematician active in the theory of finite groups, knot theory, number theory, combinatorial game theory and coding theory. He has also contributed to many branches of recreational mathematics, notably the invention of the Game of Life (the cellular automata, not the board game).
Among amateur mathematicians, he is perhaps most widely known for his contributions to combinatorial game theory, that he developed with Elwyn Berlekamp and Richard Guy.