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)

Births

• Rhodri Mawr ('the Great'), ruler of Gwynedd (Wales) (approximate date) (d. 878)
• Photius I, Patriarch of Constantinople (approximate date) (d. 891)

Deaths

• December 24 - Leo V, Byzantine Emperor (b. 775)(assassinated)
• Tang Xian Zong , emperor of China (end of reign)