Weird fiction is a subgenre of speculative fiction originating in the late 19th and early 20th centuries. Weird fiction either eschews or radically reinterprets traditional antagonists of supernatural horror fiction, such as ghosts, vampires, and werewolves. Writers on the subject of weird fiction, such as China Miéville, sometimes use "the tentacle" to represent this type of writing. The tentacle is a limb-type absent from most of the monsters of European folklore and gothic fiction, but often attached to the monstrous creatures created by weird fiction writers, such as William Hope Hodgson, M. R. James, Clark Ashton Smith, and H. P. Lovecraft.

Speculative fiction is an umbrella genre of fiction that encompasses all the subgenres that depart from realism, or strictly imitating everyday reality, instead presenting fantastical, supernatural, futuristic, or other imaginative realms. This catch-all genre includes, but is not limited to, science fiction, fantasy, horror, slipstream, magical realism, superhero fiction, alternate history, utopia and dystopia, fairy tales, steampunk, cyberpunk, weird fiction, and some apocalyptic and post-apocalyptic fiction. The term has been used for works of literature, film, television, drama, video games, radio, and their hybrids.