Babylon 5 is a five-mile long space station located in neutral space. Built by the Earth Alliance in the 2250s, it's goal is to maintain peace among the various alien races by providing a sanctuary where grievances and negotiations can be worked out among duly appointed ambassadors. A council made up of representatives from the five major space-faring civilizations - the Earth Alliance, Minbari Federation, Centauri Republic, Narn Regime, and Vorlon Empire - work with the League of Non-Aligned Worlds to keep interstellar relations under control. Aside from its diplomatic function, Babylon 5 also serves as a military post for Earth and a port of call for travelers, traders, businessmen, criminals, and Rangers.

When the Cardassian occupation of Bajor ended in 2369, the mining space-station Terok Nor was left abandoned, its systems ripped out. By invitation of the provisional Bajoran government, Starfleet stepped in to oversee the rebuilding and day-to-day operations of the newly christened Deep Space Nine. DS9 soon became a center of travel and commerce thanks to a newly found stable wormhole leading to the largely unexplored Gamma Quadrant.

It's 1999 and Moonbase Alpha has been built on the Moon to safeguard the nuclear waste shipped from Earth. On September 13, 1999, disaster strikes and the nuclear waste explodes causing a chain reaction that hurls the Moon out of Earth's orbit and into deep space. The adventures of Space:1999 begin.