1256

By place

Europe

• May 4 - Pope Alexander IV issues the papal bull Licet ecclesiae catholicae, constituting the Order of Saint Augustine at Lecceto Monastery.
• The city of Lviv, in present-day Ukraine, founded by Danylo King of Rus, is first mentioned in the written account of Chełm fire.
• Theodore II Lascaris, Byzantine Emperor, successfully concludes a military campaign started a year earlier, to recover Thrace from the Bulgarians.
• Abingdon School is founded in England.
• August 25 - In Bologna slavery and serfdom is abolished; the event is recorded in the document called Liber Paradisus.
• Roger Bacon becomes a Franciscan friar.
• The Church of Santa Costanza, Rome, is consecrated.
• The ancient Irish Kingdom of Breifne splits into East Breifne and West Breifne, after a war between the O'Reillys and the O'Rourkes.
• The War of the Euboeote Succession begins, involving most of the lords of Frankish Greece and the Republic of Venice.

  Asia

• May - The Mongol forces capture and sack Tun in Persia and massacre its people.
• June 30 - A large volcanic eruption in Harrat Rahat is associated with an Islamic prophecy.
• October - Mongol commander Baiju leads his forces in a victory over Kay Ka'us II of the Sultanate of Rum, thereby capturing Anatolia.
• November 19 - Nizari Ismaili Imam Rukn al-Din Khurshah surrendered to the invading Mongols under Hulagu while he was besieged in Maymun-Diz
• December 15 - Hulagu captures and dismantle the Alamut Castle after the surrender of the Nizari Ismaili leaders, disestablishing their state
• Hulagu Khan establishes the Ilkhanate dynasty of Persia, which will become one of four main divisions of the Mongol Empire.
• The Japanese Kenchō era ends, and the Kōgen era begins.