The 1240s was a decade that began on 1 January 1240 and ended on 31 December 1249.
|Centuries:||12th century – 13th century – 14th century|
|Decades:||1210s 1220s 1230s – 1240s – 1250s 1260s 1270s|
|Years:||1240 1241 1242 1243 1244 1245 1246 1247 1248 1249|
|Categories:||Births – Deaths – Architecture|
Establishments – Disestablishments
- 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)