Star Trek: Deep Space Nine (sometimes abbreviated to ST:DS9 or DS9) is a science fiction television program that premiered in 1993 and ran for seven seasons, ending in 1999. Rooted in Gene Roddenberry’s Star Trek universe, it was created by Rick Berman and Michael Piller, at the request of Brandon Tartikoff, and produced by Paramount Television. The main writers, in addition to Berman and Piller, included show runner Ira Steven Behr, Robert Hewitt Wolfe, Ronald D. Moore, Peter Allan Fields, Bradley Thompson, David Weddle, and René Echevarria.

A spin-off of Star Trek: The Next Generation, DS9 began while its parent series was still on the air, and there were several crossover episodes between the two shows. In addition, two Next Generation characters, Miles O'Brien and Worf, became regular members of DS9.

Unlike the other Star Trek programs, DS9 took place on a space station instead of a starship, so as not to have two series with starships at the same time. (The starship USS Defiant was introduced later in the series, but the station remained the primary setting for the show.) This made continuing story arcs and the appearance of recurring characters much more feasible. The show is noted for its well-developed characters and its original, complex plots. The series also depended on darker themes, less physical exploration of space, and an emphasis (in later seasons) on many aspects of war.

Although DS9's ratings were solid, it was never as successful as Star Trek: The Next Generation, with lower ratings than TNG received (approximately 7% versus 11% of U.S. Households according to Nielsen Ratings). In addition DS9 experienced a loss of audience over time because of an increasingly crowded television marketplace (Babylon 5, Hercules, Xena competed for timeslots), minimal promotion for DS9 while Paramount focused its efforts on its flagship Star Trek: Voyager network show, and the transition of independent stations to new networks (UPN and WB) that filled once-open slots with primetime programming (forcing DS9 into weekend or late-night slots). All of these factors combined until original programming for syndication virtually disappeared by the year 2000. Nonetheless, DS9 remained the top-rated syndicated-drama series throughout its run.

Spike in the United States, Virgin 1 in the United Kingdom, Sci Fi Channel in Australia, and La7 in Italy currently air the program.

The stable wormhole discovered by the Deep Space Nine crew is known to the Bajoran people as the Celestial Temple of their Prophets. Sisko, as discoverer of the wormhole and its inhabitants, is therefore the Emissary of Bajoran prophesy. The wormhole's other end is in the Gamma Quadrant, halfway around the galaxy from Bajor. That section of space is dominated by the malevolent Dominion. The Dominion is led by the Changelings, the race of shapeshifters to which Odo belongs. As of the beginning of the sixth season, Cardassia has joined the Dominion, and together they are waging war on the Federation and their Klingon allies. The war is quickly becoming the most costly war ever for the Federation, and the Deep Space Nine crew must fight to protect their way of life. Written by Matthew D. Wilson