|1240 by topic|
|Political entities - State leaders - Religious leaders|
|Birth and death categories|
|Births – Deaths|
|Establishments and disestablishments categories|
|Establishments – Disestablishments|
|Art and literature|
|1240 in poetry|
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- December 6 – Batu Khan and the Golden Horde sack the Ruthenian city of Kiev.
- Tuan Mash'ika, an Arab, travels and introduces Islam to Sulu.
- July 15 – Battle of the Neva: Russian prince Alexander Nevsky defeats the Swedes, saving the Novgorod Republic from a full-scale enemy invasion from the North.
- The civil war era in Norway ends.
- The Flemish village Kaprijke is recognized as a city.
- Sancho II of Portugal conquers the cities of Ayamonte and Cacella from the Muslims, as part of the Reconquista.
- June 12 – The Disputation of Paris begins at the court of Louis IX of France, where four rabbis defend the Talmud against Nicholas Donin's accusations of blasphemy.
- Saint Maurice starts to be portrayed as a Moor.
- September 29 – Margaret of England, queen consort of the Scots (d. 1275)
- Abulafia, Maltese Jewish philosopher (d. 1292)
- Pope Benedict XI (d. 1304)
- Sigerus of Brabant, French theologian (d. 1284)
- Albert the Degenerate, landgrave of Thuringia (approximate date; d. 1314)
- Peter III of Aragon, King of Aragon, Count of Barcelona and King of Valencia, very important monarch (d. 1285)
- April 11 – Llywelyn the Great, King of Gwynedd
- May 27 – William de Warenne, 5th Earl of Surrey (b. 1166)
- October 13 – Razia Sultana of Delhi (b. 1205)
- November 16 – Ibn Arabi, Andalusian Arab philosopher (b. 1165)