The Sixth Fleet served as one of the nine primary interstellar combat groups within the navy maintained by the Galactic Federation of Free Alliances government during the Second Galactic Civil War, specifically around 40 ABY.
This fleet marked the initial growth of the Galactic Alliance's naval organization, extending it beyond the original five battlegroups that constituted the core of the Fleet during the preceding era of the New Republic, a structure that likely persisted into the nascent stages of the new government.
Prior to the conclusion of 40 ABY, the Seventh, Eighth and Ninth Fleets had already been incorporated into the Alliance's order of battle.
As of 40 ABY, Admiral Nek Bwua'tu directly oversaw the Sixth Fleet, alongside the First Fleet, as they participated together in the protracted Battle of Kuat that spanned several weeks. By 44 ABY, its role had shifted to the defense of the space immediately surrounding Coruscant.