Alternate reality (or Alternative reality, UK English) often refers to parallel universes in fiction, a self-contained separate world, universe or reality coexisting with the real world, which is used as a recurring plot point or setting used in fantasy and science fiction.

Alternate reality may also refer to:

• The many-worlds interpretation of quantum mechanics, which implies the existence of parallel universes
• Multiverse, a group of multiple universes

• Alternate history, a genre of fiction consisting of stories that are set in worlds in which historical events unfold differently from the real world
• Alternate universe (fan fiction), fiction by fan authors that deliberately alters facts of the canonical universe they are writing about

• Alternate Realities (Cherryh), a 2000 anthology of science fiction by C. J. Cherryh

• Alternate Reality (series), a role-playing video game series started in 1985 with two of several intended games released
• Alternate reality game, a type of cross-media game
• Virtual reality, simulated reality

• A euphemism for "psychedelic experience"

• Metaverse, a collective virtual shared space
• Parallel universe (disambiguation)
• Separate reality (disambiguation)
• Megaverse (disambiguation)
• Multiverse (disambiguation)
• Omniverse (disambiguation)
• AR (disambiguation)
• Augmented reality
• Alternate facts