Philip José Farmer (January 26, 1918 – February 25, 2009) was an American author, principally known for his award-winning science fiction and fantasy novels and short stories. In a writing career spanning more than 60 years (1946–2008), Farmer published almost 60 novels, over 100 short stories and novellas (many expanded or combined into novels), two “fictional biographies” and numerous essays, articles and ephemera in fan publications.

Farmer is best known for his sequences of novels, 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 often mixed real and classic fictional characters and worlds and real and fake authors as epitomized by his Wold Newton family group of books. These tie all classic fictional characters together as real people and blood relatives resulting from an alien conspiracy. Such works as The Other Log of Phileas Fogg (1973) and Doc Savage: His Apocalyptic Life (1973) are early examples of literary mashup.

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