A Mighty Fortress most often refers to A Mighty Fortress Is Our God, a 1529 or 1531 hymn by Martin Luther. It may also refer to:

• A Mighty Fortress (album), a 1986 album by Steve Green
• A Mighty Fortress (game), a 1977 game published by Simulations Publications
• A Mighty Fortress (novel), a 2010 science fiction novel by David Weber
• A Mighty Fortress (Harold Covington novel), a novel by Harold Covington
• Ein feste Burg ist unser Gott, BWV 80, a chorale cantata by Johann Sebastian Bach
• A Mighty Fortress: A New History of the German People, a 2004 history work by Steven Ozment
• The Mighty Fortress, a 1955 newsreel film of Billy Graham's 1954 Crusade for Europe