| Millennium: | 1st millennium BC |
| Centuries: | 5th century BC – 4th century BC – 3rd century BC |
| Decades: | 370s BC 360s BC 350s BC – 340s BC – 330s BC 320s BC 310s BC |
| Years: | 349 BC 348 BC 347 BC 346 BC 345 BC 344 BC 343 BC 342 BC 341 BC 340 BC |
| Categories: | Births – Deaths – Architecture Establishments – Disestablishments |
In 340 BC, Philip II of Macedon led an attack on Byzantium, leaving Alexander, now aged 16, to act as regent of Macedon.