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 (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: