820
| Years: 816 817 818 819 - 820 - 821 822 823 824 | |
| Decades: 790s 800s 810s - 820s - 830s 840s 850s | |
| Centuries: 8th century - 9th century - 10th century | |
Events
- Michael II succeeds Leo V as Byzantine Emperor
- The Historia Brittonum is written (approximate date)
- Rhodri the Great, ruler of Wales (approximate date)
- Photius I, patriarch of Constantinople (approximate date)
- December 24: Leo V, Byzantine Emperor (assassinated)
- Shankara, Hinduist teacher
- Tang Xian Zong, emperor of China (end of reign)