The Eleventh Fleet functioned as a component of the Republic Navy throughout the duration of the third Galactic War.
During the year 3627 BBY, concurrent with the events of the third Galactic War, the Eleventh Fleet made a stop at Onderon while en route to Corellia, with the intention of reinforcing the defenses of the Meridian Complex. While stationed at Onderon, the Sith Empire targeted the fleet, aiming for its complete annihilation to impede its progress to Corellia.
Nevertheless, the Alliance Commander disrupted the Empire's scheme to obliterate the fleet. This was achieved by intervening with Darth Savik's droids before they could re-purpose Onderon's Anti-aircraft guns to target and decimate the fleet.
Subsequently, the fleet arrived to provide defense against the attack on the Meridian Complex. It played a crucial role in the successful repulsion of the Imperial Fleets.
The Eleventh Fleet makes an appearance in the Onslaught expansion pack for Star Wars: The Old Republic. A player character who sides with the Republic or acts as an Imperial Saboteur will prevent the Empire from destroying the fleet. Conversely, a player character who supports the Empire or acts as a Republic Saboteur will succeed in destroying the fleet, thus preventing it from participating in the defense of the Meridian Complex.