Cthulhu Mythos

The Cthulhu Mythos is a shared fictional universe, based on the work of American horror writer H. P. Lovecraft.

The term was first coined by August Derleth, a contemporary correspondent of Lovecraft, who used the name of the creature Cthulhu—a central figure in Lovecraft literature and the focus of Lovecraft's short story "The Call of Cthulhu" (first published in pulp magazine Weird Tales in 1928)—to identify the system of lore employed by Lovecraft and his literary successors. The writer Richard L. Tierney later applied the term "Derleth Mythos" to distinguish between Lovecraft's works and Derleth's later stories.

Authors writing in the Lovecraftian milieu use elements of the Mythos in an ongoing expansion of the fictional universe.