Each Galaxy-class starship, such as the U.S.S. Enterprise-D, is composed of two spacecraft systems integrated to form a single vessel. Under certain conditions, a separation maneuver can be made to allow the two components to operate independently. The two sections - the saucer module and the stardrive section (also known as the battle section) - are normally joined by a series of docking latches, numerous umbilicals, and turbolift pass-throughs. After separation, the Battle Bridge (located on Deck 8) becomes the center of operations for the stardrive section, while the Main Bridge a continues to control the saucer module.

Saucer separation can be initiated on a Galaxy-class starship in emergency situations, to protect the crew, or for tactical purposes during battle. While separation and reconnection maneuvers are generally performed by the ship's automated flight systems (controlled by the ship's computer), flight officers are expected to be able to perform the maneuvers manually - as Commander William T. Riker was instructed to do by Captain Picard during the Farpoint mission of the U.S.S. Enterprise-D.

At the planet Minos, Lieutenant Commander Geordi LaForge ordered a saucer separation of the Enterprise in order to safeguard the lives of the crew from an attack by an automated defense system. After transferring the bulk of the crew to the saucer section, LaForge used the battle section to return to the planet and rescue the away team.

During a Borg attack on the Federation, Commander Riker ordered saucer separation as a diversionary tactic to allow a shuttlecraft piloted by Lt. Commander Data and Lt. Worf to penetrate the Borg ship's shields and retrieve Locutus. After the Borg ship's destruction, Picard made note of Riker's "brilliantly unorthodox strategy" in defeating the enemy.