Lovecraftian horror, also called cosmic horror or eldritch horror, is a subgenre of horror fiction and weird fiction that emphasizes the horror of the unknowable and incomprehensible more than gore or other elements of shock. It is named after American author H. P. Lovecraft (1890–1937). His work emphasizes themes of cosmic dread, forbidden and dangerous knowledge, madness, non-human influences on humanity, religion and superstition, fate and inevitability, and the risks associated with scientific discoveries, which are now associated with Lovecraftian horror as a subgenre. The cosmic themes of Lovecraftian horror can also be found in other media, notably horror films, horror games, and comics.

Horror is a genre of fiction that is intended to disturb, frighten or scare. Horror is often divided into the sub-genres of psychological horror and supernatural horror, which are in the realm of speculative fiction. Literary historian J. A. Cuddon, in 1984, defined the horror story as "a piece of fiction in prose of variable length... which shocks, or even frightens the reader, or perhaps induces a feeling of repulsion or loathing". Horror intends to create an eerie and frightening atmosphere for the reader. Often the central menace of a work of horror fiction can be interpreted as a metaphor for larger fears of a society.