Fourth dimension or 4D can mean a number of things: Science
- Fourth dimension, the concept of a fourth spatial dimension
- Spacetime, the concept of time forming a fourth dimension
Literature
- The Fourth Dimension, a non-fiction book by Rudy Rucker
- The Fourth Dimension, a book by Dr. David Yonggi Cho
- The Four-Dimensional Nightmare, a collection of science fiction short stories by J. G. Ballard
Music
- The Fourth Dimension, an album by Hypocrisy
- Fourth Dimension, an album by Stratovarius
- Fourth Dimension, an album by BBC Radiophonic Workshop composer Paddy Kingsland
- Fourth Dimension Records, a UK record label
- The 4th Dimension, a record label
- "The 4th Dimension", a song by Devo from their album Shout.
Computing
- The Fourth Dimension, a publisher of computer games
- 4th Dimension, a relational database management system
Other
- Fourth dimension (lottery), a lottery draw of 4-digit numbers, in Singapore and Malaysia
- Four dimensionalism, a philosophical view that the past, present and future are all "equally real"
