Decades: 470s BC 460s BC 450s BC 440s BC 430s BC - **420s BC** - 410s BC 400s BC 390s BC 380s BC 370s BC

Years: 429 BC 428 BC 427 BC 426 BC 425 BC - **424 BC** - 423 BC 422 BC 421 BC 420 BC 419 BC

- December 24 - King Artaxerxes I of Persia is last mentioned alive in inscription. Three of his sons soon rival each other for the throne as Xerxes II, Sogdianus and Darius II of Persia.
- Battle of Delium

**Deaths**

- December - Artaxerxes I, king of Persia.