Updated: September 12, 2021

Star Trek is an American science fiction television series created by Gene Roddenberry that follows the adventures of the starship USS Enterprise (NCC-1701) and its crew. It later acquired the retronym of Star Trek: The Original Series (Star Trek: TOS or simply TOS) to distinguish the show within the media franchise that it began.

The show is set in the Milky Way galaxy, roughly during the 2260s. The ship and crew are led by Captain James T. Kirk (William Shatner), first officer and science officer Spock (Leonard Nimoy), and chief medical officer Leonard McCoy (DeForest Kelley). Shatner's voice-over introduction during each episode's opening credits stated the starship's purpose:

Space—the final frontier. These are the voyages of the starship Enterprise. Its five-year mission—to explore strange new worlds—to seek out new life and new civilizations—to boldly go where no man has gone before.

The series was produced from September 1966 to December 1967 by Norway Productions and Desilu Productions, and by Paramount Television from January 1968 to June 1969. Star Trek aired on NBC from September 8, 1966, to June 3, 1969, and was actually seen first on September 6, 1966, on Canada's CTV network. Star Trek's Nielsen ratings while on NBC were low, and the network canceled it after three seasons and 79 episodes. Several years later, the series became a bona fide hit in broadcast syndication, remaining so throughout the 1970s, achieving cult classic status and a developing influence on popular culture. Star Trek eventually spawned a franchise, consisting of six additional television series, thirteen feature films, numerous books, games, and toys, and is now widely considered one of the most popular and influential television series of all time.