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

Years: 434 BC 433 BC 432 BC 431 BC 430 BC - **429 BC** - 428 BC 427 BC 426 BC 425 BC 424 BC

- Battle of Chalcis - Chalcidians and their allies defeat Athens.
- Battle of Naupactus - Phormio defeats the Peloponnesian fleet.
- An outbreak of plague kills over one-third of the population of Athens.

**Deaths**