827
| Years: 823 824 825 826 - 827 - 828 829 830 831 | |
| Decades: 790s 800s 810s - 820s - 830s 840s 850s | |
| Centuries: 8th century - 9th century - 10th century | |
Events
- Succession of Pope Valentine, then Pope Gregory IV.
- Arabs invade Sicily.
- The royal ceremonial centre at Copán is abandoned.
- Chalid Ben Abdulmelik and Ali Ben Isa measure the size of the Earth.
- Saint Cyril, scholar, theologian and linguist
- Emperor Montoku of Japan
- Pope Eugene II
- September: Pope Valentine