|829 by topic|
|Ab urbe condita||1582|
|Balinese saka calendar||750–751|
|Chinese calendar||戊申年 (Earth Monkey)
3525 or 3465
— to —
己酉年 (Earth Rooster)
3526 or 3466
|- Vikram Samvat||885–886|
|- Shaka Samvat||750–751|
|- Kali Yuga||3929–3930|
|Japanese calendar||Tenchō 6
|Minguo calendar||1083 before ROC
|Seleucid era||1140/1141 AG|
|Thai solar calendar||1371–1372|
955 or 574 or −198
— to —
956 or 575 or −197
|Wikimedia Commons has media related to 829.|
- October 2 – Emperor Michael II dies after a 8-year reign in Constantinople, and is succeeded by his 16-year-old son Theophilos, as sole emperor of the Byzantine Empire. He continues his father's ideology of iconoclasm.
- October – Battle of Thasos: Saracens from the newly found Emirate of Crete almost annihilate the Byzantine fleet at Thasos, close to the coast of Thrace. The Cyclades and other islands in the Aegean Sea are pillaged.
- Emperor Louis the Pious appoints his 6-year-old son Charles (by his second wife Judith) as ruler of the Frankish subkingdom Alamannia, enraging his eldest son and co-emperor Lothair I, who begins an insurrection.
- Viking chieftain Halfdan the Black becomes king of Agder (modern Norway). He expands his realm through military conquest and political negotiations, dividing the kingdom of Vestfold with his half-brother Olaf.
- Giustiniano Participazio, doge of Venice, dies after a 2-year reign, and is succeeded by his younger brother Giovanni Participazio. He continues the work of Giustiniano, in construction of St. Mark's Basilica.
- King Egbert of Wessex invades Mercia, ousts his rival Wiglaf, and attempts to rule directly from Wessex. He is recognized as overlord (bretwalda) of other English kingdoms.
- Winter – Battle of the River Dore: Egbert of Wessex leads his army against the Northumbrians as far as Dore, were he clashes with King Eanred of Northumbria.
- Ansgar, Frankish abbot of Corvey (modern Westphalia), is appointed missionary to Sweden by Louis the Pious, at the request of the Swedish king Björn at Haugi.
- The city of Wiesbaden (Germany) is first mentioned by Einhard, biographer of former emperor Charlemagne (approximate date).
- September 8 – Ali al-Hadi, 10th Shia Imam (approximate date)
- Al-Nasa'i, Muslim scholar and hadith compiler (approximate date)
- Lu Yan, chancellor of the Tang Dynasty (d. 874)
- Yahya I, Muslim sultan (d. 864)
- June 1 – Li Tongjie, general of the Tang Dynasty
- July 30 – Shi Xiancheng, general of the Tang Dynasty
- October 2 – Michael II, emperor of the Byzantine Empire (b. 770)
- Abu al-Razi Muhammad, Muslim governor
- Cináed mac Mugróin, king of Uí Failghe
- Cui Zhi, chancellor of the Tang Dynasty (b. 772)
- Giustiniano Participazio, doge of Venice
- Leibulf of Provence, Frankish nobleman
- Li Yi, Chinese poet (or 827)
- Li You, general of the Tang Dynasty
- Muiredach mac Ruadrach, king of Leinster
- 'Umayr ibn al-Walid, Muslim governor
- Wei Chuhou, chancellor of the Tang Dynasty (b. 773)
- Zheng Yin, chancellor of the Tang Dynasty (b. 752)
- Timothy E. Gregory, A History of Byzantium, (Blackwell Publishing Ltd, 2010), p. 227.
- Treadgold, Warren (1988). The Byzantine Revival, 780–842, Stanford University Press, p. 268. ISBN 0-8047-1462-2.
- Lamb, H. H. (1977) Climate: Present, Past and Future: Climatic History and the Future Vol 2, Methuen and Co. Ltd., London.