Diocletian was a Roman emperor who ruled from 284–305 AD.
Diocletian may also refer to:
Architecture
- Aqueduct of Diocletian, a Roman aqueduct near Split, Croatia
- Baths of Diocletian, a bath complex in Rome, Italy
- Camp of Diocletian, a military complex at Palmyra, Syria
- Diocletian's Palace, an ancient fortress which forms the core of the modern town of Split, Croatia
- Diocletian window, large windows characteristic of Ancient Roman bath complexes
Other uses
- Diocletian (band), a war metal band from New Zealand
- Dioclesian, a tragicomic semi-opera by Henry Purcell