|Covid-19|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 – Sighvatr Sturluson and Sturla Sighvatsson are defeated by Kolbeinn ungi Arnórsson and Gissur Þorvaldsson in the Battle of Örlygsstaðir 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.
Founder of the Nasrid dynasty, Mohammed I ibn Nasr, begins Alhambra complex on the site of a pre-Islamic fortress.
Thowadra Monastery is founded in Bhutan.
The Khmers are expelled from Luang Phrabang in Laos.
The Sukhothai kingdom is founded in Thailand.
May 1 – Magnus Lagabøte, king of Norway (d. 1280)
November – Henry de Montfort, son of Simon de Montfort, 6th Earl of Leicester (d. 1265)
Nizamuddin Auliya, Indian Sufi saint (d. 1325)
Frederick III, Duke of Lorraine (d. 1302)
Meinhard II of Gorizia-Tyrol (d. 1295)
Shri Madhvacharya, Vaishnavite saint and founder of the Dvaita School (d. 1317)
Joan of England, Queen of Scotland, wife of Alexander II of Scotland (b. 1210)
Prince Yuri II of Vladimir (b. 1189)
March 19 – Henry I the Bearded, Duke of Lower Silesia (b. c. 1165)
June 9 – Peter des Roches, bishop of Winchester
Al-Kamil, Ayyubid sultan of Egypt
Hugh le Despenser I, English nobleman
Year 1238 (MCCXXXVIII) was a common year starting on Friday (link will display the full calendar) of the Julian calendar.