Capital ship
From Halopedia, the Halo wiki
Capital Ships are the "most important" and "largest" warships; the ones with the heaviest firepower and armor. There is usually no formal criterion for the classification, but it is a useful concept when thinking about strategy, for instance to compare relative naval strengths in a theater of operations without having to get bogged down in the details of tonnage and gun variants. A capital ship is generally a leading or primary ship in a fleet, battlegroup, or Strike Force.
Covenant
These are the classifications of Covenant warships known to fall under the Capital Ship category:
UNSC
These are the classifications of UNSC Warships known to fall under the Capital Ship category: