"USS Callister" is the first episode of the fourth series of the anthology series Black Mirror. Written by series creator Charlie Brooker and William Bridges and directed by Toby Haynes, it first aired on Netflix, along with the rest of series four, on 29 December 2017.

The episode follows Robert Daly (Jesse Plemons), a reclusive but gifted programmer and co-founder of a popular massively multiplayer online game who is bitter over the lack of recognition of his position from his coworkers. He takes out his frustrations by simulating a Star Trek–like space adventure within the game, using his co-workers' DNA to create sentient digital clones of them. Acting as the captain of the USS Callister starship, Daly is able to order his co-workers around, bend them to his will, and mistreat them if they get out of line. When Daly brings newly hired Nanette Cole (Cristin Milioti) into his game, she encourages the other clones to revolt against Daly.

In contrast to most Black Mirror episodes, "USS Callister" contains overt comedy, and it has many special effects. As a fan of Star Trek, Bridges was keen to introduce many details from the show into "USS Callister", though the episode was conceived mostly with The Twilight Zone's 1961 episode "It's a Good Life" and the Viz character Playtime Fontayne in mind. The episode's reception was overwhelmingly positive, with reviewers praising the allusions to Star Trek, the acting, and the cinematography. Critics saw the episode as being about male abuse of authority, and compared Daly to contemporary events surrounding internet bullies and sexual abuse committed by Harvey Weinstein. In 2018, the episode won four Primetime Emmy Awards, including Outstanding Television Movie and Outstanding Writing for a Limited Series, Movie, or Dramatic Special, and was nominated for three other Emmy Awards. A sequel episode is planned as part of the seventh season of Black Mirror.