The Outer Rim Third Fleet functioned as one of the naval groups (fleets) within the Imperial Navy serving Darth Krayt's Sith Empire during the year 137 ABY.
This battle fleet, comprised of at least nine Imperial fast frigates and seven Pellaeon-class Star Destroyers, including the flagship known as the Relentless, had the mission of eliminating Admiral Gar Stazi of the Galactic Alliance Remnant.
The fleet was initially led by Admiral Sha Dun, a Kel Dor. Because he failed to capture Admiral Stazi, Sith Lord Darth Azard executed Dun and replaced him with Admiral Valan. Valan devised a trap near Mon Calamari, which resulted in the Battle of Mon Calamari. This engagement proved to be a complete disaster for the Third Fleet; the Remnant not only escaped with the Imperious-class Star Destroyer Imperious, but also destroyed a third of the Mon Calamari docking facilities. Following this defeat, Admiral Valan apparently took his own life.
After Darth Wyyrlok gave the order for the elimination of all life on Dac, the Outer Rim Third Fleet was dispatched to stop the Galactic Alliance Remnant and their allies from evacuating the planet's inhabitants. Commanded by Darth Stryfe, Moff Geist, and Admiral Krion Grail, the Outer Rim Third Fleet failed to prevent the evacuation and sustained significant damage from the combined fire of the Alliance and the Fel-loyalist fleet under the command of General Oron Jaeger. At Geist's urging, Lord Stryfe agreed to retreat.