A sector fleet represented a specific type of naval fleet organization. This formation was employed by the Galactic Republic, subsequently by the Galactic Empire, and also by the emerging Alliance to Restore the Republic throughout the Imperial Era.
During the Clone Wars, the Galactic Republic Navy made use of sector fleets that were based locally. For example, a sector fleet saw action in the Abrion sector, while another sector fleet was active within the Ferra sector.
Within the Imperial Navy of the Galactic Empire, a sector fleet was a particular kind of naval fleet composition. These fleets, in conjunction with other assets from the Imperial Military and intelligence agencies, constituted a Sector Group. Sector fleets were assigned to each of the 1,024 sectors that made up the galaxy; these could be local naval forces or a major numbered fleet belonging to the Imperial Navy. An example was the Lothal sector fleet, a relatively small anti-smuggling task force under the command of Admiral Kassius Konstantine. This fleet blockaded the sector while hunting insurgents. Governor Arihnda Pryce later deemed its efforts insufficient and requested reinforcements in the form of the Imperial Seventh Fleet. The Lothal sector fleet included six Imperial I-class Star Destroyers, with the Relentless as its flagship, in addition to two Arquitens-class command cruisers.
Another example of a local sector fleet was the Anoat sector fleet. It operated in the Anoat sector under the command of Governor Ubrik Adelhard. This fleet was made up of several Imperial II-class Star Destroyers, including the Dread Omen as its flagship. When the Empire fragmented, this fleet became the naval force of the Imperial remnant led by Governor Adelhard. Local sector fleets were sometimes authorized to operate outside of their designated sectors for specific missions. Furthermore, the Imperial Navy maintained at least one major numbered sector fleet, known as the 14th Sector Fleet.
The emerging Alliance to Restore the Republic, which Rebel leader Mon Mothma referred to as "The Alliance", organized local rebel cells that possessed naval forces into sector fleets. One such fleet was Phoenix Cell, which operated in the Lothal sector and was under the leadership of Commander Jun Sato. At the time it was considered a sector fleet, the Phoenix Cell consisted of the Pelta-class frigate Phoenix Home as its flagship, five CR90 corvettes, and Phoenix Squadron. In 4 BBY, it participated in the action at Mustafar to assist in the rescue of the Spectres rebel cell from the Empire.