|Centuries:||4th century – 5th century – 6th century|
|Decades:||370s 380s 390s – 400s – 410s 420s 430s|
|Years:||398 399 400 – 401 – 402 403 404|
- Pope Innocent I succeeds Pope Anastasius I.
- The Vandals start their westward trek from Dacia and Hungary (or 400).
- The Visigoths begin to attack the northernmost reaches of Italy, causing destruction in the countryside.
- Kumarajiva arrives in Changan.
- Western Roman Empire general Stilicho leads an extensive campaign against the Vandals in Rhaetia.
- Synod of Turin
- for more information, see Category:401 deaths.