Clifford Donald Simak (August 3, 1904 – April 25, 1988) was an American science fiction writer. He won three Hugo Awards and one Nebula Award.The Science Fiction Writers of America made him its third SFWA Grand Master,[4] and the Horror Writers Association made him one of three inaugural winners of the Bram Stoker Award for Lifetime Achievement.[5] He is associated with the pastoral science fiction subgenre.