Byzantine-Arab War: Emperor Theophilos signs an armistice for peace with the Abbasid Caliphate. He offers Caliph Al-Ma'mun 100,000 gold dinars, in return for 7,000 Byzantine prisoners.
June – Lothair I, eldest son of Emperor Louis the Pious, joins the rebellion of his brothers Pepin I and Louis the German, with the assistance of Archbishop Ebbo. Louis is forced to abdicate, on the plains of Rothfield (near Colmar).
Mojmir I, Moravian duke, expels Prince Pribina from his homeland. He unifies Great Moravia (modern Czech Republic) and becomes the first known ruler of the Moravian Slavs, who founds the House of Mojmir (approximate date).
Galindo Aznárez I, Frankish count, usurps the Catalan counties (pagi) of Pallars and Ribagorza, in the Spanish March (modern Spain), a buffer zone between the Pyrenees and the Ebro River.
August 7 – Caliph Al-Ma'mun dies after a 20-year reign. He is succeeded by his half-brother Al-Mu'tasim, as ruler of the Abbasid Caliphate.
Ibn Hisham, Muslim historian, collects oral traditions that form the basis for the biography of the Islamic prophet Muhammad.
Emperor Junna abdicates the throne, after a 10-year reign. He is succeeded by his nephew Nimmyō, as the 54th emperor of Japan.
Irmgard, Frankish abbess (or 830)
Kocel, Slavic prince (approximate date)
Luo Yin, Chinese statesman and poet (d. 910)
Yi Zong, emperor of the Tang Dynasty (d. 873)
May 7 – Ibn Hisham, Muslim historian
July 20 – Ansegisus, Frankish abbot (or 834)
August 9 – Al-Ma'mun, Muslim caliph (b. 786)
Conchobar mac Donnchada, High King of Ireland
Diarmait mac Tommaltaig, king of Connacht (Ireland)
Dou Yizhi, chancellor of the Tang Dynasty
Du Yuanying, chancellor of the Tang Dynasty (b. 769)
Enravota, ruler of the Bulgarian Empire (approximate date)
García Galíndez (the Bad), count of Aragon
Nagabhata II, ruler of the Gurjara-Pratihara Dynasty
Song Shenxi, chancellor of the Tang Dynasty
Yuthog Yontan Gonpo, Tibetan high priest (b. 708)
Year 833 (DCCCXXXIII) was a common year starting on Wednesday (link will display the full calendar) of the Julian calendar.