|Centuries:||12th century – 13th century – 14th century|
|Decades:||1200s 1210s 1220s – 1230s – 1240s 1250s 1260s|
|Years:||1234 1235 1236 – 1237 – 1238 1239 1240|
- Thomas II of Savoy becomes count of Flanders.
- Elbląg, Poland is founded.
- Representatives of all 4 khanates lead 150000 Mongol, Turkish and Persian troops into Europe.
- The Mongols invade Russia.
- Gualdo Tadino, Italy, is destroyed by fire.
- The County of Artois is founded in France.
- Baldwin II becomes Latin Emperor of Constantinople.
- Conrad IV of Germany becomes King of Germany.
- The Livonian Brothers of the Sword unite with the Teutonic Knights.
- Frederick II, Holy Roman Emperor defeats Lombard League at Battle of Cortenuova
- A major fire destroys some 30,000 dwellings in the Chinese capital city of Hangzhou.
- April 15 – Richard Poore, English ecclesiastic
- June 6 – John de Scotia, 9th Earl of Huntingdon
- John of Brienne, king of Jerusalem and Latin Emperor of Constantinople (born c. 1148)
- Jordanus Nemorarius, German scientist
- Pons de Capduelh, French troubadour
- September 23 – Snorri Sturluson, Icelandic historian, poet and politician (born c.1178)