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