The Necronomicon is a fictional grimoire appearing in the stories by horror writer H. P. Lovecraft and his followers. It was first mentioned in Lovecraft's 1924 short story "The Hound", written in 1922, though its purported author, the "Mad Arab" Abdul Alhazred, had been quoted a year earlier in Lovecraft's "The Nameless City". Among other things, the work contains an account of the Old Ones, their history, and the means for summoning them.
Other authors such as August Derleth and Clark Ashton Smith also cited it in their works; Lovecraft approved, believing such common allusions built up "a background of evil verisimilitude." Many readers have believed it to be a real work, with booksellers and librarians receiving many requests for it; pranksters have listed it in rare book catalogues, and a student smuggled a card for it into the Yale University Library's card catalog.
Capitalizing on the notoriety of the fictional volume, real-life publishers have printed many books entitled Necronomicon since Lovecraft's death.