A term used in discussing science fiction, a Big Dumb Object (BDO) is a mysterious artifact (usually alien) in a story which generates an intense sense of wonder just by being there; to a certain extent, the term deliberately deflates this. J.G. Ballard's short story, Report on an Unidentified Space Station (1982) is an exploration of the metaphor of the BDO: in each succcessive report, the artifact's estimated size increases, people get lost within it, and the reader eventually realises that the mysterious abandoned artifact is the Universe itself..

Big Dumb Objects in science fiction include:

• Iain M. Banks' Excession
• Greg Bear's Thistledown asteroid-starship in Eon
• Algis Budrys' Killing Machine found on the Moon in Rogue Moon
• Arthur C. Clarke's monolith in 2001: A Space Odyssey
• Arthur C. Clarke's Rama
• Peter F. Hamilton's Sleeping God in The Night's Dawn Trilogy
• Fred Hoyle's Black Cloud
• Michael Crichton's Sphere in Sphere
• Alistair Reynold's Cerberus/Hades in Revelation Space
• Bob Shaw's Orbitsville, and many other Dyson spheres
• Charles Sheffield's Heritage Universe.
• Clifford D. Simak's abandoned machine-world in Limiting Factor (1949)
• The Vorlon "thirdspace gate" in the Babylon 5 television movie Thirdspace