1238

By place

Europe

• March 4 - Mongol invasion of Rus - Battle of the Sit River: The Mongol Hordes of Batu Khan defeat the Rus', under Yuri Vsevolodovich of Vladimir-Suzdal.
• August 21 - Battle of Örlygsstaðir: Sighvatr Sturluson and Sturla Sighvatsson are defeated by Kolbeinn ungi Arnórsson and Gissur Þorvaldsson, for control of Iceland.
• September 28 - James I of Aragon captures the city of Valencia from the Moors, who retreat to Granada.
• The seat of the Patriarch of Aquileia is transferred to Udine.
• Simon de Montfort marries Eleanor, sister of Henry III of England.
• The Livonian Order gives Northern Estonia back to Denmark, with the Treaty of Stensby.
• The Mongols seize Moscow, at the time a small town.
• Peterborough Cathedral is consecrated.
• The founder of the Nasrid Dynasty, Muhammad I of Granada, begins Alhambra Complex on the site of a pre-Islamic fortress.
• Thowadra Monastery is founded in Bhutan.
• Communal uprisings in Santiago de Compostela against the archbishop.

  Asia

• The Khmers are expelled from Luang Phrabang in Laos.
• The Sukhothai Kingdom is founded in Thailand.
• The Nizari Imam Ala al-Din Muhammad and the Abbasid caliph Al-Mustansir send a joint diplomatic mission to the European kings Louis IX of France and Edward I of England to forge a Muslim–Christian alliance against the Mongols, but this is unsuccessful.