Call of Cthulhu is a horror roleplaying game based upon the writings of Howard Phillips Lovecraft and a few others. Lovecraft wrote during the 1920s and 1930s, and he became a cult figure before dying in 1937.

Since then his stature as an author has grown, and now he is generally recognized as the major American horror-story writer of the twentieth century. His fiction ranges from pure science fiction to gothic horror. His non-fiction includes a history of Quebec, the commentary Supernatural Horror in Literature, and a gigantic correspondence (five volumes of his letters have been issued by Arkham House publishers). Author-publisher August Derleth coined the term "Cthulhu Mythos", but the commonality of plot and suggestion behind the term remains an enduring monument to Lovecraft. A series of his stories share as elements certain diabolical entities (especially the Great Old Ones) and books of arcane lore and great power, first among them the ghastly Necronomicon. The Cthulhu Mythos is named after a god-like entity, Cthulhu (kuh-THOO-loo is the easiest, though not the best way to say it). Many Great Old Ones, Cthulhu included, are prophesied to wake and to lay waste to the world "when the stars are right".

These tales fired the imagination of other authors, mostly protégés and friends of Lovecraft, and soon they were adding to his mythology. Today, Cthulhu stories are still being written by heirs to Lovecraft's literary legacy.

The Call of Cthulhu RPG continues the tradition. Young writers from around the world have contributed to or independently written well over a hundred new books of scenarios and other supplements. Besides English, translations and original new supplements also appear in French, German, Japanese, Italian, Polish, and Spanish.

In imitation of Lovecraft, who also wrote excellent tales of horror unconnected with the Mythos, not all Call of Cthulhu scenarios need explore the Mythos: plenty of scope for horrible motive and despicable deed exists apart from it.