- June 22 - Byzantine Emperor Michael I is defeated in a war against the Bulgarians.
- July 12 - A revolt puts Leo V on the throne; Michael becomes a monk. Beginning of the Second Iconoclastic Period.
- Louis the Pious crowned co-emperor with his father Charlemagne.
- Baghdad school of astronomy opened by Al Mamon.
- Third Council of Tours: priests are ordered to preach in the vernacular (either Vulgar Latin or German)
- Abu Nuwas, poet