Fort Deen is an United Nations Space Command military base located on Arcadia. It is named after a famous war hero, Colonel Deen, who broke a Covenant siege. Nothing else is known about the base, or its role in the war at this time.
- The Halo Wars multiplayer level with the same name takes place around and presumably within the fort.
- Its name is a reference to one of Ensemble Studios' senior designers, Tim Deen.