Entertainment
- The Citadel (novel), a 1937 novel by A. J. Cronin
- The Citadel (film), a 1938 film based on the novel
- The Citadel (1960 British miniseries), British adaptation
- The Citadel (1960), American movie adaptation
- La Cittadella (1964), Italian miniseries adaptation
- The Citadel (TV series), British 1983 BBC television adaption
- La Cittadella (2003), another Italian miniseries adaptation
- The Citadel (Comics), a fictional alien empire from DC Comics' Omega Men
- A Combine headquarters, in the game Half-Life 2, on Earth's City 17
- An immense space station and the heart of galactic civilization, in the game Mass Effect
- A Dragonlance novel by Richard A. Knaak, in the Classics Series
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