Star Trek: Deep Space Nine is a science fiction television series that debuted in 1993 and ran for seven seasons, finishing in 1999. Based on Gene Roddenberry’s Star Trek, it was created by Rick Berman and Michael Piller, and produced by Paramount Pictures. The main title is sometimes shortened to ST:DS9, or simply DS9.

DS9 began while Star Trek: The Next Generation was still on the air, and there were several crossover episodes between the two series. Unlike its predecessor, DS9 was unabashedly original and often broke the rules laid down by Gene Roddenberry. In contrast with the other series, Deep Space Nine took place on a space station instead of a starship. It also relied heavily on continuing story arcs, many recurring characters, and darker themes. The main writers for DS9, in addition to creators Berman and Piller, included Ronald D. Moore, Peter Allen Fields, Ira Steven Behr, Robert Hewitt Wolfe, Joe Menosky, René Echevarria. Richard Manning, and Hans Beimler.

Originally conceived in 1991, shortly before Gene Roddenberry’s death, DS9 chronicles the events surrounding space station Deep Space 9, a former Cardassian ore-processing station, which has recently been placed under joint control of the United Federation of Planets and Bajor, the planet it formerly orbited. The station was repositioned to monitor traffic through the recently discovered Bajoran wormhole. As a result of the wormhole, the station became a cornerstone of interstellar trade and political activity in the Bajoran sector particularly, and the quadrant at large. This unique premise makes it the first, and so far only, Star Trek series not to be set aboard a starship.

According to co-creator Berman, he and Piller had considered setting the new series on a colony on an alien planet, but they felt a space station would both appeal more to viewers and save money due to the high cost of on-location shooting for a land-based show. However, they were certain that they did not want the show to be set aboard a starship because The Next Generation was still in production at the time and, in Berman’s words, it "just seemed ridiculous to have two shows—two casts of characters—that were off going where no man has gone before."

In the first episode, the crew discovers the presence of a nearby stable wormhole, which provides immediate transportation to and from the distant Gamma Quadrant; this makes the station an important strategic asset, as well as a vital center of commerce with a largely-unexplored area of space. Inside the wormhole live aliens who exist beyond time and do not understand the linear nature of other lifeforms. To the people of Bajor, these aliens are the Prophets and the wormhole itself is the long-prophesied Celestial Temple. Commander Benjamin Sisko, who discovers the wormhole with Jadzia Dax, becomes revered as the Emissary of the Prophets, a spiritual role with which he is initially extremely uncomfortable.

Deep Space Nine was well received by critics, with TV Guide describing it as "the best acted, written, produced, and altogether finest" Star Trek series. However, some fans grew dissatisfied with the show’s generally darker themes and objected to the notion of a series set on a space station. Fans of the series call themselves “Niners,” after a baseball team of the same name, which appeared in the seventh-season episode “Take Me Out to the Holosuite”.

The show was never the ratings success that its predecessor was, due to a variety of factors—not the least of which was the fact that it was the “middle child of the franchise” competing against the last few seasons of Next Generation’s successful run and the beginning of Star Trek: Voyager’s series on the new UPN network. Nonetheless, it remained the top rated first-run syndicated drama series throughout most of its run and was successful enough to ensure that Paramount launched two more Star Trek series—Star Trek: Voyager and Enterprise—following its conclusion. It is best remembered for its well-developed characters and its original, complex plots.

- From Wikipedia