Diocles may refer to:
- Diocles (mathematician) (c. 240 BC – c. 180 BC), Greek mathematician and geometer
- Diocles (mythology), one of the first priests of Demeter
- Diocles of Carystus, 4th century BC Greek physician
- Diocles of Cnidus, Greek philosopher who wrote a work quoted by Eusebius
- Diocles of Corinth, winner of the stadion race of the 13th Olympic Games in 728 BC
- Diocles of Magnesia, Greek writer on ancient philosophers quoted many times by Diogenes Laertius
- Diocles of Messenia, winner of the stadion race of the 7th Olympic Games in 752 BC
- Diocles of Peparethus, Greek historian in the 3rd century BC
- Diocles of Syracuse, (fl. 413-408 BC), Greek lawgiver in the city-state of Syracuse
- Diocletian (244–311), Roman emperor formerly named Diocles
- Gaius Appuleius Diocles, Roman charioteer