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 presented in 1966 and are awarded in four categories for literary works of different lengths. 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.

The Nebula Awards are one of the best known and most prestigious science fiction and fantasy awards and The Guardian called them "the most important of the American science fiction awards", together with the Hugo Awards. Winning works have been published in special collections, and winners and nominees are often noted as such on the books' covers. SFWA identifies the awards by the year of publication, that is, the year prior to the year in which the award is given.

For lists of winners and nominees for each Nebula category, see the list of categories below.

The Nebula Awards are given annually by the Science Fiction and Fantasy Writers of America (SFWA) for the best science fiction or fantasy fiction published during the previous year. To be eligible for consideration works must be published in English in the United States. Works published in English elsewhere in the world are also eligible provided they are released on either a website or in an electronic edition. The awards are not limited to American citizens or members of SFWA. Works translated into English are also eligible.

There are no written rules as to which works qualify as science fiction or fantasy, and the decision of eligibility in that regard is left up to the nominators and voters, rather than to SFWA.

The winner receives a trophy but no cash prize; the trophy is a transparent block with an embedded glitter spiral nebula and gemstones cut to resemble planets. The trophy itself was designed for the first awards by J. A. Lawrence, based on a sketch by Kate Wilhelm, and has remained the same ever since.

Nebula Award nominees and winners are chosen by members of the SFWA. Works are nominated each year between November 15 and February 15 by published authors who are members of the organization, with the six works that receive the most nominations forming the final ballot. Additional nominees are possible in the case of ties. Members then vote on the ballot throughout March, and the final results are presented at the Nebula Awards ceremony in May. Authors are not permitted to nominate their own works, though they can decline nominations. Ties in the final vote are broken, if possible, by the number of nominations the works received.

The first Nebulas were given in 1966, for works published in 1965. The idea for such an award, funded by the sales of anthologies collecting the winning works, was proposed by SFWA secretary-treasurer Lloyd Biggle, Jr. in 1965. The idea was based on the Edgar Awards, presented by the Mystery Writers of America, and the idea to have a ceremony at which to present them was prompted by the Edgar and Hugo Awards. The initial ceremony consisted of four literary awards, for Novels, Novellas, Novelettes, and Short Stories, which have been presented every year since. A Script award was also presented from 1974 to 1978 under the names Best Dramatic Presentation and Best Dramatic Writing and again from 2000 through 2009 as Best Script, but after 2009 it was again removed and replaced by SFWA with the Ray Bradbury Award. In 2018, a new Game Writing category was added, for writing in video and tabletop games.