The Liber Ivonis, or Book of Eibon, is a fictitious book of black magic mentioned in the Cthulhu Mythos stories of H. P. Lovecraft, Clark Ashton Smith, and others. Eibon, its author, was a wizard from the land of Hyperborea. According to the stories, only incomplete fragments of the original are thought to exist, although there are translations in English, French, and Latin. Liber Ivonis is the title of the Latin translation.

The Book of Eibon is mentioned in a number of Lovecraft's stories, such as "The Haunter of the Dark".

The horror film The Beyond, directed by the late Lucio Fulci, features the Book of Eibon, though the film's story is not Lovecraftian. The book's appearance is more of a tribute to Lovecraft.