Fan fiction or fanfiction is fictional writing written in an amateur capacity as fans, unauthorized by, but based on an existing work of fiction. The author uses copyrighted characters, settings, or other intellectual properties from the original creator as a basis for their writing. Fan fiction ranges from a couple of sentences to an entire novel, and fans can both keep the creator's characters and settings and/or add their own. It is a form of fan labor. Fan fiction can be based on any fictional subject. Common bases for fan fiction include novels, movies, musical groups, cartoons, anime, manga, and video games.
Fan fiction is rarely commissioned or authorized by the original work's creator or publisher and is rarely professionally published. It may infringe on the original author's copyright, depending on the jurisdiction and on legal questions such as whether or not it qualifies as "fair use". Attitudes of authors and copyright owners of original works to fan fiction have ranged from indifference to encouragement to rejection. Copyright owners have occasionally responded with legal action.