From Halopedia, the Halo wiki
Fleetmaster, occasionally rendered as Fleet Master, is one of the highest titles given to individuals in command of fleets within the Covenant military. On the eve of the Great Schism, the High Prophet of Truth granted the title to several Jiralhanae.
One of the varying degrees of command titles within the Covenant fleet, the title of fleetmaster was given to the officer in command of a fleet. The title was originally only assigned to Sangheili officers within the Covenant fleet, though towards the end of the Human-Covenant War, the High Prophet of Truth promoted several Jiralhanae to the title of fleetmaster in preparation for his plans to remove the Sangheili from the Covenant. Following the empire's collapse during the Great Schism, some Sangheili still held the title of fleetmaster.
Wearing golden combat harnesses to signify their command position, fleetmasters normally utilize a large warship as their flagship, such as a CAS-class assault carrier or ORS-class heavy cruiser. Following the fall of the Covenant, some fleetmasters have found that ancient Carrack merchant cruisers are surprisingly capable and resilient troop and materiel transports in modern conflicts. When Voro 'Mantakree was promoted from major to a fleetmaster, Imperial Admiral Xytan 'Jar Wattinree bestowed a middle name upon him, making his name Voro Nar 'Mantakree. However, a middle name is not given to all fleetmasters. Fleetmasters can order tweaks on starships for their fleet during the ship's construction.
List of appearances