|Centuries:||4th century – 5th century – 6th century|
|Decades:||390s 400s 410s – 420s – 430s 440s 450s|
|Years:||425 426 427 – 428 – 429 430 431|
- Bonifacius, Roman governor of Africa, asks for help from the Vandals in his revolt.
- Flavius Felix is elected consul for the Western Empire.
- King Gunderic, age 49, dies after a reign of 21 years. He is succeeded by his half-brother Genseric.
- King Vortigern asks Germanic warriors to help him strengthen his position in Britain. He hires Saxons as mercenaries to fight against the Picts and the Scots beyond Hadrian's Wall.
- Chlodio, king of the Salian Franks, invades Northern Gaul. He defeats the Roman army at Cambrai. He extends his kingdom south to the River Somme. Tournai (modern Belgium) becomes his residence.
- Artaxias IV, last king of Greater Armenia, is deposed by Bahram V. The Arshakuni Dynasty ends and the kingdom becomes a province of the Persian Empire.
- April 10 – Nestorius is made patriarch of Constantinople. He preaches a new doctrine that will be called Nestorianism. It comes under immediate attack from pope Celestine I and Cyril of Alexandria.
- Hydatius becomes bishop of Aquae Flaviae in Gallaecia (modern Chaves) in Portugal.
- John succeeds Theodotus as patriarch of Antioch, and gives his support to Nestorius.
- Euthymius the Great builds a monastery in Palestine, near the Dead Sea.