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.
February 9 – Mongol conquest of the Jin dynasty: In the Siege of Caizhou, Song Dynasty Chinese and Mongolian armies occupy the Jurchen capital at Caizhou and the Emperor Aizong of Jin commits suicide, marking the collapse of the Jin dynasty.
Upon the death of Knut Långe, the deposed Erik Eriksson returns as king of Sweden, possibly after a small war between the two of them. It is also possible that Knut dies of natural causes and Erik peacefully then returns as king.
Pope Gregory IX calls for a crusade against Bosnia, and replaces the Bogumil Bosnian Bishop with a Catholic Dominican German, Johann.
King Andrew II of Hungary proclaims herzeg Coloman as Ban of Bosnia, who passes it on to Prijezda, a cousin of Ban Matej Ninoslav (1234 to 1239), despite Matej being the legitimate Ban of Bosnia.
Sancho II of Portugal conquers the cities of Aljustrel and Mértola over the Muslims.
Saint Dominic is canonized.
Pope Gregory IX releases the Nova Compilatio Decretalium or Decretales Gregorii IX.
Abaqa Khan, Mongol emperor of Persia (d. 1282)
Imam Fauziah Nawawi, prominent Muslim scholar
Ippen, Japanese monk (d. 1289)
April 16 – Richard Marshal, 3rd Earl of Pembroke (b. 1191)
June 18 – Emperor Chūkyō of Japan (b. 1218)
July 19 – Floris IV (Count of Holland) (b. 1210)
Alan, Lord of Galloway
Stefan Radoslav, King of Serbia (b. 1192)
Knut Långe, usurper to the Swedish throne since 1229
Year 1234 (MCCXXXIV) was a common year starting on Sunday (link will display the full calendar) of the Julian calendar.
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