Citadel

The Citadel may refer to:
 * Battle of the Citadel - The last major battle to be fought in the Human-Covenant War.
 * Covenant citadel - The Covenant structure used in ''Halo Wars.
 * Citadel Charum - A Precursor structure on Charum Hakkor.
 * Citadel (level) - One of the Halo 3 DLC maps.
 * Citadel Skull (achievement) - Claimed by obtaining the Citadel Skull.
 * Citadel (Trevelyan) - A Forerunner city inside the shield world Trevelyan.
 * Installation 00 Citadel - The Forerunner structure located on the Ark.