Deep Space Nine (DS9) is a large space station around a kilometer in diameter located in the Bajor system. It is also the title of the Star Trek series depicting events closely tied to the station.
Formerly known as Terek Nor by its Cardassian builders, DS9 is the nearest Federation facility to an unusually large and stable wormhole leading to the Gamma Quadrant. It was originally an ore processing facility for Cardassian mining operations on Bajor.
The Federation has equipped DS9 with numerous phaser banks and 5,000 photon torpedoes.
DS9 was a critical facility for the Federation because it controlled the Alpha Quadrant opening of the Bajoran Wormhole. It was also the main base of operations after Starbase 375.