Seventh Fleet
From Halopedia, the Halo wiki
The Seventh Fleet was a UNSC Fleet of starships of unknown size.
It participated in the Second Battle of Earth on November 3, 2552, and, in conjunction with the Second and Sixteenth Fleets, was engaged in major skirmishes with the Covenant fleet in Earth orbit.
It was mentioned by Sergeant Laura "Smokes" Tanner while piloting Blue Team to the Centennial Orbital Elevator.