For broader historical context, see 13th century.

Events

Europe

• September - The Empire of Nicaea defeats the Principality of Achaea at the Battle of Pelagonia, ensuring the eventual reconquest of Constantinople in 1261.
• December 4 - Kings Louis IX of France and Henry III of England agree to the Treaty of Paris, in which Henry renounces his claims to French-controlled territory on continental Europe (including Normandy) in exchange for Louis withdrawing his support for English rebels.
• The famous frescoes of the Boyana Church in Bulgaria are completed (the church and its murals are now a UNESCO World Heritage Site).
• The German cities of Lübeck, Wismar, and Rostock enter into a pact to defend against pirates of the Baltic Sea, laying the groundwork for the Hanseatic League.

Asia

• Lannathai, a kingdom in the north of Thailand, is founded by King Mengrai.
• The Goryeo kingdom in Korea surrenders to invading Mongol forces.
• The Chinese era Kaiqing begins and ends in the Northern Song Dynasty of China.
• The Japanese Shoka era ends, and the Shogen era begins.

Births

• Pietro Cavallini, Italian painter
• Richard Og de Burgh, 2nd Earl of Ulster

Deaths

• May 29 - King Christopher I of Denmark
• Möngke Khan, Grand Khan of the Mongol Empire
• Dunaba Dibbalemi , king of the Kanem-Bornu Empire of Africa
• Ezzelino da Romano III, ruler of Verona, Vicenza, and Padua
• Thomas II of Savoy
• Richard Og de Burgh, 2nd Earl of Ulster
• Matthew Paris, Benedictine monk and chronicler

See also

List of state leaders in 1259