A shared universe is a fictional setting that is used by several authors, script writers, or game designers. There are usually certain characters who "belong" to a specific author, and anyone using those characters in a story or game must obtain permission from the original creator. The setting can be used by anyone, as can certain of the background characters.

The best known examples of a shared universe are probably the Star Trek and Star Wars franchises, which use many authors to create stories about the characters and worlds. Two examples of novel "universes" include Thieves' World and Wolf Creek, both of which used a "stable" of authors to create stories about a fictional town and its characters.