Events

• 20 March - Pope Gregory IX excommunicates Frederick II, Holy Roman Emperor.

Undated

• Frederick II, Holy Roman Emperor conducts the Siege of Faenza.
• The main tower of Lincoln Cathedral collapses.

Births

• June 17 - King Edward I of England (d. 1307)
• December 17 - Kujo Yoritsugu, Japanese shogun (d. 1256)
• Peter III of Aragon (d. 1285)
• John II, Duke of Brittany (d. 1305)
• Ippen, Japanese monk (d. 1289)

Deaths

• March 3 - Vladimir III Rurikovich, Grand Prince of Kiev (b. 1187)
• March 20 - Hermann von Salza, fourth Grand Master of the Teutonic Knights
• March 28 - Emperor Go-Toba of Japan (b. 1180)
• Cormac mac Art O Melaghlain, King of Meath

Ongoing Events

• Mongol invasion of Rus (1237–1240)