The Nebula Awards annually recognize the best works of science fiction or fantasy published in the United States. The awards are organized and awarded by the Science Fiction and Fantasy Writers Association (SFWA), a nonprofit association of professional science fiction and fantasy writers. They were first given in 1966 at a ceremony created for the awards, and are given in four categories for different lengths of literary works. A fifth category for film and television episode scripts was given 1974–78 and 2000–09, and a sixth category for game writing was begun in 2018. In 2019 SFWA announced that two awards that were previously run under the same rules but not considered Nebula awards—the Andre Norton Award for Middle Grade and Young Adult Fiction and the Ray Bradbury Award for Outstanding Dramatic Presentation—were to be considered official Nebula awards. The rules governing the Nebula Awards have changed several times during the awards' history, most recently in 2010. The SFWA Nebula Conference, at which the awards are announced and presented, is held each spring in the United States. Locations vary from year to year.

Science fiction is a genre of speculative fiction, which typically deals with imaginative and futuristic concepts such as advanced science and technology, space exploration, time travel, parallel universes, and extraterrestrial life. It is related to fantasy, horror, and superhero fiction and contains many subgenres. Its exact definition has long been disputed among authors, critics, scholars, and readers.