Science-fiction opera is a subgenre of science fiction. It refers to operas whose subject-matter fits in the science fiction genre. Like science-fiction literature, science-fiction operas may be set in the future and involve intergalactic travel or alien invasion. Other science-fiction operas focus on a dystopian view of the future. Like Lorin Maazel's opera 1984, they may be based on a previously written science fiction book.