| Agis III Ἄγις | |
|---|---|
| King of Sparta | |
| Reign | 2 August 338 – 331 BC |
| Predecessor | Archidamus III |
| Successor | Eudamidas I |
| Died | 331 BC (aged c. 29) Megalopolis |
| Father | Archidamus III |
Agis III (Greek: Ἄγις, died 331 BC) was the eldest son of Archidamus III, and the 21st Eurypontid king of Sparta between 338 and 331 BC. He tried to lead a revolt against Macedonian hegemony over Greece, but was defeated by Antipater—Alexander the Great's regent in Greece—at the Battle of Megalopolis in 331 BC, where he died.