Season one is set in the year 2258 aboard a five-mile-long, totally self-sufficient United Nations-like space station. Babylon 5 is where humans and aliens try to work out their differences peacefully, in neutral territory full of mystery, suspense, and adventure. The space outpost is a hotbed of interplanetary intrigue, conspiracies, and betrayals among myriad life-forms living and working together.

In season two, Babylon 5 gets a controversial new leader as the station prepares to serve as the last defense against a terrifying race known as the Shadows.

It is now the year 2259. Five hostile federations dominate the outermost regions of space. This season, Babylon 5's captain declares the station an independent state and forms a war council to battle the evil Shadows – and their allies on Earth.

In season four, the station continues to serve as a refuge for heroes, thieves, and rare and exotic beings in a time of uneasy peace and the constant threat of war. The space station and its allies finally engage the powerful Shadows in a tremendous showdown, while the station's captain strives to expose far-reaching corruption on Earth. Also, Sheridan and Delenn's alliance – both personal and political – signals a new age of peace in the universe.

In 2262, longstanding conflicts between telepaths and normal humans lead to a major clash on the space station. A new captain takes over, and Sheridan continues Babylon 5's peacekeeping mission by forming the InterStellar Alliance.