An enormous space station discovered by several different sentient races in the galaxy. Home to 13.1 million people, the Citadel is the seat of the Citadel Council, the supreme authority in the galaxy, which consists of one Turian, one Salarian, one Asari and, most recently, one Human.

Although it was originally thought to have been created by the Protheans, the Citadel was in fact created by the Reapers to serve as a gathering point for all sentient races in the galaxy. Its exact age is unknown, but it predates any current sentient race. The Citadel is ocated in the Serpent Nebula.

Shepard returns to the Citadel to speak with Admiral Anderson, who applauds his motives but is worried by his decision to side with Cerberus. A number of loyalty missions take place on the Citadel, and a handful of side missions are available.