Events

• March 18 – Battle of Chmielnick: The Mongols defeat a feudal Polish army.

• April 9 – Battle of Liegnitz: The Mongols under the command of Baidar, Kadan and Orda Khan, defeat the feudal Polish nobility, including the Knights Templar.

• April 11 – Battle of Mohi: Batu Khan and Subutai defeat Béla IV of Hungary.

• April 27 – Battle of Sajo: The Mongols defeat Bela IV of Hungary.

• May 10 – Battle of Cameirge: The Milesian Irish Septs of the O'Donnells from Donegal, the O'Neills from Armagh and the O'Dohertys of Connacht defeat the last Tuathe de Danaan Sept the MacLochlainns of Tir-owen and Inish-Owen under Domhnall MacLochlainn.

• August 29 – after Henry III's invasion of Wales, the Treaty of Gwerneigron is signed by him and Dafydd ap Llywelyn, curbing the latter's authority and denying him royal title.

• October 25 – Pope Celestine IV succeeds Pope Gregory IX as the 179th pope.

• Snorri Sturluson, Icelandic saga writer, is murdered by Gissur Þorvaldsson, an emissary of King Haakon IV of Norway.

• Emperor Lizong of Song China accepts the Neo-Confucian teachings of the late Zhu Xi, including his commentary on the Four Books. This will have an impact upon the philosophical schools of surrounding countries as well, including Korea, Japan, and Vietnam.

Births

• September 4 – King Alexander III of Scotland (d. 1286)

• Eleanor of Castile, queen of Edward I of England (d. 1290)

Deaths

• April 9 – Duke Henry II of Poland

• May 10 – Domhnall MacLochlainn, High King – Ard Ri of all Ireland

• June 24 – Ivan Asen II of Bulgaria

• August 10 – Eleanor, Fair Maid of Brittany (b. c. 1184)

• August 22 – Pope Gregory IX

• September 23 – Snorri Sturluson, Icelandic historian, poet and politician (b. 1178)

• September 26 – Fujiwara no Teika, Japanese poet

• November 10 – Pope Celestine IV

• December 1 – Isabella of England, wife of Frederick II, Holy Roman Emperor (b. 1214)

• Bernardo di Quintavalle

• Eleanor, Fair Maid of Brittany

• Mary, Countess of Blois (b. 1200)

• Ögedei Khan

• Valdemar II of Denmark (b. 1170)

• Baba Ishak, charismatic preacher (b. c. 1239)