The UNSC Cydonia was a Cydonia-class fleet carrier of the UNSC Navy, and was the lead vessel of the Cydonia-class carriers, the first of the fleet carrier classifications to be constructed. She would serve as the flagship of Admiral Douglas A. Davidson, Commander-in-Chief of the UNSC Fifth Fleet during the Galactic Era. While serving as Davidson's command vessel, the UNSC Cydonia would be attached to Task Force Phoenix, the flag task force of the Fifth Fleet, during its deployment to Dashan.