Year 1234 (MCCXXXIV) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar.
|Ab urbe condita||1987|
|Balinese saka calendar||1155–1156|
|English Regnal year||18 Hen. 3 – 19 Hen. 3|
|Chinese calendar||癸巳年 (Water Snake)|
3930 or 3870
— to —
甲午年 (Wood Horse)
3931 or 3871
|- Vikram Samvat||1290–1291|
|- Shaka Samvat||1155–1156|
|- Kali Yuga||4334–4335|
|Japanese calendar||Tenpuku 2 / Bunryaku 1|
|Minguo calendar||678 before ROC|
|Thai solar calendar||1776–1777|
1360 or 979 or 207
— to —
1361 or 980 or 208
- King Canute II (the Tall) dies after a 5-year reign. His rival, Eric XI (the Lisp and Lame), returns as ruler of Sweden (possibly after a civil war between the two of them). It is also possible that Canute dies of natural causes, and Eric peacefully then returns as king.
- King Andrew II of Hungary proclaims his son, Coloman of Galicia, as ruler (or ban) of Bosnia, who passes it on to Prijezda, a cousin of Matej Ninoslav, despite Matej being the legitimate ruler of Bosnia.
- Reconquista: King Sancho II of Portugal conquers the cities of Aljustrel and Mértola from the Moors.
- February 9 – Mongol–Jin War: The Mongol army led by Ögedei Khan captures the Jin capital at Caizhou, after a two-month siege (see Siege of Caizhou). Emperor Aizong of Jin abdicates the throne to Wanyan Chenglin, a descendant of the Jin imperial clan. After the Mongol and Song forces have breached the city walls, Aizong tries to escape, but commits suicide to avoid being captured. This marks the end of the Jin Dynasty (Great Jin).
- The Manden region rises against the Kaniaga Kingdom. This is the beginning of a process that will lead to the rise of the Mali Empire.
- November – Pope Gregory IX proclaims war on the city of Rome after a local revolt forces him into exile. He issues the papal bull Rachel suum videns, calling for a new crusade to the Holy Land.
- Lund Cathedral in Sweden is heavily damaged in a catastrophic fire. Large donations are made to the church, to rebuild the cathedral.
- Abaqa Khan, Mongol ruler of the Ilkhanate (d. 1282)
- Christina of Norway, Norwegian princess (d. 1262)
- Coloman Asen I, emperor (tsar) of Bulgaria (d. 1246)
- Conrad of Ascoli, Italian friar and missionary (d. 1289)
- Ippen (or Zuien), Japanese Buddhist monk (d. 1289)
- Manuel of Castile, Spanish prince (infante) (d. 1283)
- Margaret of Holland, Dutch noblewoman (d. 1276)
- Ou Shizi, Chinese Confucian scholar (d. 1324)
- January 7 – Robert of Auvergne, bishop of Clermont
- February 9
- Aizong of Jin, Chinese emperor (b. 1198)
- Mo of Jin (or Hudun), Chinese emperor
- April 7 – Sancho VII (the Strong), king of Navarre
- April 16 – Richard Marshal, English nobleman (b. 1191)
- May 7 – Otto I, German nobleman and knight (b. 1180)
- June 18 – Chūkyō, emperor (tennō) of Japan (b. 1218)
- July 19 – Floris IV, Dutch nobleman and knight (b. 1210)
- July 29 – William Pinchon, French prelate and bishop
- August 7 – Hugh Foliot, bishop of Hereford (b. 1155)
- August 31 – Go-Horikawa, emperor of Japan (b. 1212)
- September 6 – Milo of Nanteuil, bishop of Beauvais
- September 26 – Eudes II of Ham, French nobleman
- Abu Muhammad Salih, Almohad Sufi leader (b. 1155)
- Alan fitz Roland (or Galloway), Scottish nobleman
- Baha ad-Din ibn Shaddad, Arab historian (b. 1145)
- Canute II (the Tall), king of Sweden (House of Folkung)
- Helen of Galloway, Scottish noblewoman and heiress
- Hugh de Neville, English Chief Forester and sheriff
- Ibn al-Farid, Arab poet, writer and philosopher (b. 1181)
- Minamoto no Ienaga, Japanese waka poet (b. 1170)
- Nasir ad-Din Mahmud (or Mahmud II), Zengid ruler
- Renard II (or Renaud), French nobleman and knight
- Rhys ap Rhys (the Younger), ruler of Deheubarth
- Robert III (Gasteblé), French nobleman (b. 1185)
- Shihab al-Din 'Umar, Persian Sufi scholar (b. 1145)
- William of Andres, French abbot and historian
- Zhang Yuansu, Chinese physician and writer
- ^ Picard, Christophe (2000). Le Portugal musulman (VIIIe-XIIIe siècle. L'Occident d'al-Andalus sous domination islamique. Paris: Maisonneuve & Larose. p. 110. ISBN 2-7068-1398-9.
- ^ Beck, Sanderson. "Liao, Xi Xia, and Jin Dynasties 907–1234". China 7 BC to 1279.
- ^ Hywel Williams (2005). Cassell's Chronology of World History, p. 138. ISBN 0-304-35730-8.