Utopia

Utopia (from the 1516 novel by Thomas More usually known by that name) designates a culture depicted in fiction or non-fiction, which is presented by the creator as being or approaching an ideal of human organization. (Some critics will use the term "utopian" to disparage an allegedly excessively idealistic concept or project.)

Science fiction and fantasy, for obvious reasons, are ideal media in which to present utopias.