1240s

The 1240s was a decade that began on 1 January 1240 and ended on 31 December 1249. It is distinct from the decade known as the 125th decade which began on January 1, 1241 and ended on December 31, 1250.

• Batu Khan and the Golden Horde sack the Ruthenian city of Kiev.
• Mandinka prince Sundiata Keita defeats Sosso king Soumaoro Kanté at the Battle of Kirina, beginning the Mali Empire.
• July 15, 1240 – Russian prince Alexander Nevsky defeats the Swedes in the Battle of the Neva, saving Russia from a full-scale enemy invasion from the North.
• End of the civil war era in Norway.
• Saint Maurice is started to be portrayed as Moor.
• April 5, 1241 – Mongols of Golden Horde under the command of Subotai defeat feudal Polish nobility, including Knights Templar, in the battle of Liegnitz
• April 27, 1241 – Mongols defeat Bela IV of Hungary in the battle of Sajo.

• Abulafia, Maltese Jewish philosopher (died 1292)
• Pope Benedict XI (died 1304)
• Stephen V of Hungary (died 1272)
• Sigerus of Brabant, French theologian (died 1284)
• Albert the Degenerate, landgrave of Thuringia (approximate date; died 1314)

• April 11, 1240 – Llywelyn the Great, King of Gwynedd
• Ibn Arabi, Andalusian Arab philosopher
• Jacques de Vitry, French historian and theologian (born c. 1180)
• William de Warenne, 6th Earl of Surrey (born 1166)