|834 by topic|
|Ab urbe condita||1587|
|Balinese saka calendar||755–756|
|Chinese calendar||癸丑年 (Water Ox)|
3530 or 3470
— to —
甲寅年 (Wood Tiger)
3531 or 3471
|- Vikram Samvat||890–891|
|- Shaka Samvat||755–756|
|- Kali Yuga||3934–3935|
|Japanese calendar||Tenchō 11 / Jōwa 1|
|Minguo calendar||1078 before ROC|
|Seleucid era||1145/1146 AG|
|Thai solar calendar||1376–1377|
960 or 579 or −193
— to —
961 or 580 or −192
Year 834 (DCCCXXXIV) was a common year starting on Thursday (link will display the full calendar) of the Julian calendar.
- March 1 – Emperor Louis the Pious is restored as sole ruler of the Frankish Empire. After his re-accession to the throne, his eldest son Lothair I flees to Burgundy.
- Danish Vikings raid the trading settlement of Dorestad (present-day Wijk bij Duurstede), located in the southeast of the province of Utrecht (modern Netherlands).
- Summer – The Viking ship of Oseberg near Tønsberg (modern Norway) is buried in a mound, during the Viking Age (approximate date).
- The first mention is made of the Jona River ('the cold one') in Switzerland (approximate date).
- King Óengus II dies after a 14-year reign. He is succeeded by his nephew Drest IX, as ruler of the Picts.
- July 20 – Ansegisus, Frankish abbot and advisor of former emperor Charlemagne, dies at Fontenelle Abbey in Normandy (or 833).
- Aud the Deep-Minded, Icelandic queen
- Euthymius I, Ecumenical Patriarch of Constantinople (d. 917)
- Lady Shuiqiu, wife of Qian Kuan (d. 901)
- Mo Xuanqing, Chinese scholar
- Pi Rixiu, Chinese poet (approximate date)
- Robert, Frankish nobleman (d. 866)
- Tan Quanbo, Chinese warlord (d. 918)
- July 20 or 833 – Ansegisus, Frankish abbot
- Adelchis I, duke of Spoleto (Italy)
- Cellach mac Brain, king of Leinster (Ireland)
- Fridugisus, Anglo-Saxon abbot (approximate date)
- Gaucelm, Frankish nobleman
- Nasr ibn 'Abdallah, Muslim governor
- Odo I, Frankish nobleman
- Óengus II, king of the Picts
- Robert III, Frankish nobleman (b. 800)
- Wang Chengyuan, Chinese general (b. 801)
- Wang Tingcou, general of the Tang Dynasty
- William, Frankish nobleman