|Centuries:||12th century · 13th century · 14th century|
|Decades:||1210s · 1220s · 1230s · 1240s · 1250s · 1260s · 1270s|
|Years:||1237 · 1238 · 1239 · 1240 · 1241 · 1242 · 1243|
|1240 by topic|
|State leaders – Sovereign states|
|Birth and death categories|
|Births – Deaths|
|Establishments and disestablishments categories|
|Establishments – Disestablishments|
|Art and literature|
|1240 in poetry|
|Ab urbe condita||1993|
|English Regnal year||24 Hen. 3 – 25 Hen. 3|
|Chinese calendar||己亥年 (Earth Pig)|
3936 or 3876
— to —
庚子年 (Metal Rat)
3937 or 3877
|- Vikram Samvat||1296–1297|
|- Shaka Samvat||1161–1162|
|- Kali Yuga||4340–4341|
|Japanese calendar||En'ō 2 / Ninji 1|
|Minguo calendar||672 before ROC|
|Thai solar calendar||1782–1783|
|Wikimedia Commons has media related to 1240.|
- 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 over 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.
- 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. (dead in 1285)
- April 11 – Llywelyn the Great, King of Gwynedd
- November 10 – Ibn Arabi, Andalusian Arab philosopher (b. 1165)
- William de Warenne, 5th Earl of Surrey (b. 1166)
- Picard, Christophe (2000). Le Portugal musulman (VIIIe-XIIIe siècle. L'Occident d'al-Andalus sous domination islamique. Paris: Maisonneuve & Larose. p. 110. ISBN 2-7068-1398-9.