1255

Events

Europe

Western Europe

* August - The final Cathar stronghold in southern France falls, eliminating their last refuge since the Roman Catholic Church began the Albigensian Crusade to crush the sect in 1209.
* The death of Little Saint Hugh of Lincoln prompts the persecution of Jews in England, based on the blood libel.
* Lisbon becomes the capital of the Kingdom of Portugal.
* The Gothic cathedral at Bourges, France, is completed. It is now a UNESCO World Heritage Site.
* A survey of royal privileges is conducted, which is included in the Hundred Rolls, an English census seen as a follow up to the Domesday Book completed in 1086; the Hundred Rolls is later completed with two larger surveys in 1274/1275 and 1279/1280.

Central and Eastern Europe

* May - William of Rubruck from Constantinople returns to Cyprus from his missionary journey to convert the Tatars of central and eastern Asia, his efforts having been unsuccessful.
* Königsberg (now Kaliningrad) is founded by the Teutonic Knights in Prussia and named in honour of king Ottokar II of Bohemia.
* Theodore II Lascaris, Byzantine Emperor (in exile in the Empire of Nicaea), conducts a military campaign to recover Thrace from the Bulgarians. He concludes the task successfully a year later in 1256.
* The Duchy of Bavaria is split into Upper and Lower Bavaria.
* The German state of Nassau is divided, not to be reunited until 1806.
* King Béla IV of Hungary grants Banská Bystrica the municipal rights of a royal town.

Asia

* Hulagu Khan is dispatched by his brother Möngke Khan to destroy the remaining Muslim states in southwestern Asia.

Births

* Albert I of Germany, Holy Roman Emperor (d. 1308)
* William de Ros, 2nd Baron de Ros, claimant to the crown of Scotland (d. 1317)
* Duccio di Buoninsegna, Sienese painter (d. 1319)
* Grand Prince Andrey of Gorodets (approximate date; d. 1304)
* Adolf of Nassau-Weilburg, King of the Romans (approximate date; d. 1298)

Deaths

* May 1 - Walter de Gray, English prelate and statesman
* Little Saint Hugh of Lincoln (b. 1247)
* Jarler, Archbishop of Sweden
* Sundiata Keita, semi-historical hero and founder of the Mali Empire (approximate date; b. c. 1190)
* Batu Khan, Mongol ruler and founder of the Blue Horde