Seventh Fleet
From Halopedia, the Halo wiki
A UNSC fleet of unknown size that was active in the Second Battle of Earth as of November 3 2552. Sergeant Laura "Smokes" Tanner, while piloting Blue Team to the Centennial Orbital Elevator, mentioned that recently the Covenant fleet had engaged it together with the Second and Sixteenth Fleets fleet in major skirmishes most likely in orbit around Earth or in the Sol System. Whether the fleet remains intact is unknown.
