Star Trek: Deep Space Nine (sometimes abbreviated to DS9) is a science fiction television series set in the Star Trek universe in the Milky Way galaxy, in the years 2369–2375. In contrast to other Star Trek TV shows, it primarily takes place on a space station rather than a starship, so as not to have two series with starships in the same time period; the series ran concurrently with Star Trek: The Next Generation during its first two seasons and with Star Trek: Voyager for the remainder of its run. The starship USS Defiant was introduced in season 3, but the Deep Space Nine space station remained the show's primary setting.
The show is noted for its well-developed characters, original and complex plots, religious themes, and for starring the only black captain in any of the televised Star Trek incarnations. Rather than following the classical Star Trek focus of space exploration, the show often showcased complex and darker social themes, and in later seasons, an emphasis on many aspects of war.
DS9 premiered in 1993 and ran for seven seasons until 1999. Although rooted in Gene Roddenberry's Star Trek universe, it was the first Trek spin off created without Roddenberry's direct involvement, although he did give the concept his blessing shortly before his death in 1991.
DS9 began while Star Trek: The Next Generation was still on the air, and there were a few cameos featuring characters from either show (such as Picard's appearance in the DS9 pilot). The station appeared in TNG during the sixth-season episode "Birthright". In addition, two Next Generation characters, Miles O'Brien and (from season 4 onwards) Worf, became regular members of DS9. The station also appeared in the first part of the Voyager pilot episode, "Caretaker".