The Necronomicon, also referred to as the Book of the Dead, or under a purported original Arabic title of Kitab al-Azif, is a fictional grimoire appearing in stories by the 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.

A grimoire is a textbook of magic, typically including instructions on how to create magical objects like talismans and amulets, how to perform magical spells, charms, and divination, and how to summon or invoke supernatural entities such as angels, spirits, deities, and demons. In many cases, the books themselves are believed to be imbued with magical powers, although in many cultures, other sacred texts that are not grimoires have been believed to have supernatural properties intrinsically. The only contents found in a grimoire would be information on spells, rituals, the preparation of magical tools, and lists of ingredients and their magical correspondences. In this manner, while all books on magic could be thought of as grimoires, not all magical books should be thought of as grimoires.