Philip José Farmer was an American author, principally known for his award-winning science fiction and fantasy novels and short stories.

Farmer is best known for his novel sequences, especially the World of Tiers (1965–93) and Riverworld (1971–83) series. He is noted for the pioneering use of sexual and religious themes in his work, his fascination for — and reworking of — the lore of celebrated pulp heroes, and occasional tongue-in-cheek pseudonymous works written as if by fictional characters. Farmer also remixed classic fictional characters, worlds, and both real and fake authors, epitomized with his Wold Newton family group of books that tie all classic fictional characters together as real people and blood relatives resulting from an alien conspiracy; his works such as The Other Log of Phileas Fogg and Doc Savage: His Apocalyptic Life make Farmer the ultimate grandfather of the modern literary mashup.

Literary critic Leslie Fiedler compared Farmer to Ray Bradbury, describing both as "provincial American eccentrics" who "strain at the classic limits of the [science fiction] form," but found Farmer distinctive for his capacity "to be at once naive and sophisticated in his odd blending of theology, pornography, and adventure."