Space fleets were fleets, consisting of spaceships, which operated in outer space. (TV: The Wheel in Space)
Many space-faring factions operated in fleets such as the Dalek Fleet, (TV: Resurrection of the Daleks) the Cyber-Fleet, Cyber-Armada and Cyber Legions of the Cybermen, (TV: Silver Nemesis, A Good Man Goes to War, COMIC: Assimilation²) and the Sontarans' Battle Fleets. (TV: The Sontaran Stratagem)
In 1881, Alpha Centauri offered to a send a fleet to assist the Ice Warriors on Mars. (TV: Empress of Mars)
The Shansheeth operated Funeral Fleets. (TV: Death of the Doctor)
Gleda Ley-Sooth Marka Jinglatheen described her ship as "the finest in the fleet". (COMIC: Doctormania)
Colonel Manton of the Church had a fleet ready to protect the space station Demons Run. During the Battle of Demons Run, the Eleventh Doctor had pair of Spitfires take out the station's communications array to prevent an automatic distress call from being sent to the fleet. (TV: A Good Man Goes to War)
In a parallel universe, the United Federation of Planets operated Starfleet. During their invasion of this universe, the Cybermen combined their fleet with that of the Borg to form the Borg-Cyberman Fleet. (COMIC: Assimilation²)