Centuries: 5th century BC - 4th century BC - 3rd century BC
- Battle of Lake Vadimo: The Romans defeat the Etruscans.
- Macedonian king Antigonus founded Antigonea, later known as Nicaea and Iznik (approximate year)
- Agathocles, tyrant of Syracuse, leads a counterstrike against Carthage
- Antigonia Troas (later known as Alexandria Troas) and Antigoneia (later known as Nicaea) are founded by Antigonus I of Macedon
- Aratus, Macedonian Greek mathematician, astronomer, meteorologist, botanist and poet (possibly born in 315 BC)
- Aristarchus, Greek astronomer and mathematician