|822 by topic|
|Ab urbe condita||1575|
|Balinese saka calendar||743–744|
|Chinese calendar||辛丑年 (Metal Ox)
3518 or 3458
— to —
壬寅年 (Water Tiger)
3519 or 3459
|- Vikram Samvat||878–879|
|- Shaka Samvat||743–744|
|- Kali Yuga||3922–3923|
|Japanese calendar||Kōnin 13
|Minguo calendar||1090 before ROC
|Seleucid era||1133/1134 AG|
|Thai solar calendar||1364–1365|
948 or 567 or −205
— to —
949 or 568 or −204
|Wikimedia Commons has media related to 822.|
- Thomas the Slav, Byzantine general (tourmarchos) and usurper, continues his revolt against Emperor Michael II. He unsuccessfully besieges Constantinople, while his fleet is destroyed by Michael's Byzantine navy, using Greek fire. Khan Omurtag of Bulgaria sends a relief army, and defeats the rebels at the Battle of Kedoutos (near Heraclea).
- Emperor Louis I performs public penance for causing his nephew Bernard's death 4 years earlier, at his palace of Attigny (Ardennes), before Pope Paschal I, and the Frankish nobles (this to restore harmony and re-establish his authority).
- King Ceolwulf I of Mercia invades Powys (Wales), but is beaten back by King Cyngen. He destroyes the fortress of Deganwy, and takes the kingdom later under his control (approximate date).
- Al-Hakam I, Umayyad emir of Córdoba, dies after a 26-year reign. He is succeeded by his son Abd al-Rahman II, who begins a military campaign against King Alfonso II of Asturias in Al-Andalus (modern Spain).
- Kim Heon-chang launches a short-lived rebellion in Silla, which gains control over much of the southern and western Korean Peninsula.
- February 6 – Ukit Took becomes the last ruler (ajaw) of the Mayan city-state Copán (modern Guatemala).
- Al-Mutawakkil, Muslim caliph (d. 861)
- Ibn Abi Asim, Muslim Sunni scholar (or 821)
- Minamoto no Tōru, Japanese poet (d. 895)
- Xuefeng Yicun, Chinese Chan master (d. 908)
- June 26 – Saichō, Japanese Buddhist monk (b. 767)
- Al-Hakam I, Muslim emir of Córdoba (b. 771)
- Al-Waqidi, Muslim historian and biographer
- Denebeorht, bishop of Worcester
- Eigil of Fulda, Bavarian abbot
- Gregory Pterotos, Byzantine general (strategos)
- Kim Heon-chang, Silla aristocrat and rebel leader
- Li Yijian, chancellor of the Tang Dynasty (b. 756)
- Tahir ibn Husayn, founder of the Tahirid Dynasty
- Tian Bu, general of the Tang Dynasty (b. 785)
- Winiges, duke of Spoleto (Italy)