Tetrarch may refer to:
- Tetrarchs, the four co-emperors of the Roman Empire instituted by the Emperor Diocletian
- Tetrarchy (Judea), formed by the sons of Herod the Great
- Tetrarch (Greek rank)
- Tetrarch (Macedonian rank)
- Tetrach (novel), a 2003 novel by Ian Irvine
- Tetrarch tank, a British light tank of World War II
- The Tetrarch, a Thoroughbred racehorse
- The Tetrarchs of Ancient Thessaly under Philip II of Macedon
- The Tetrarchs of Galatia in Asia Minor
- Tetrarches, a rank in the Byzantine army
- Tetrarch, a 1981 fantasy novel by Alex Comfort