Within the Imperial Navy, the title of Fleet Admiral was accorded to the commanding officer of a major fleet within a Sector Group. A Fleet Admiral answered directly to the High Admiral in charge of Navy operations within their Sector, who was normally the Moff or Grand Moff of the sector; his own command might be a front-line Superiority Fleet, an Assault Fleet or Bombard Fleet for planetary suppression operations, or a logistical Deepdock Fleet or Support Fleet. The commanding officer of Death Squadron under Darth Vader was also apparently a Fleet Admiral.
A Fleet Admiral was a very important member of the military hierarchy within a Sector, with authority over multiple Systems Forces commanded by subordinate Systems Admirals. However, it is not certain from the available evidence whether Fleet Admiral was a formally constituted rank in the Imperial hierarchy, or a title accorded to an officer commanding a fleet-level force, regardless of his substantive rank: for example, Michael Unther apparently served as the commanding Admiral of a Sector Fleet while still holding the substantive rank of Captain or Commander.