|Centuries:||12th century – 13th century – 14th century|
|Decades:||1220s 1230s 1240s – 1250s – 1260s 1270s 1280s|
|Years:||1250 1251 1252 – 1253 – 1254 1255 1256|
- July 6 – Mindaugas is crowned as King of Lithuania.
- July – William II, Count of Holland defeats the Flemish army at Westkapelle.
- A series of naval wars begins between the Italian city-states of Genoa and Venice, which will continue sporadically until 1371.
- King Henry III of England meets with English nobles and church leaders to reaffirm the validity of the Magna Carta.
- Pope Innocent IV returns to Rome, having left nine years earlier in 1244 to depose Frederick II, Holy Roman Emperor, and being unable to return until after Frederick's death due to the agitation throughout Europe caused by that action.
- Having rebuffed the armed forces of Conrad IV of Germany, Pope Innocent IV offers Sicily to Edmund, son of King Henry III of England.
- Galicia becomes a vassal state to the expanding Mongol Empire.
- January 19 – Dogen, Japanese founder of the Soto school of Zen Buddhism
- August 11 – Clare of Assisi, Italian follower of Francis of Assisi (born 1194)
- October 9 – Robert Grosseteste, English statesman and theologian
- Wenceslaus I, King of Bohemia
- Theobald IV of Champagne (born 1201)
- Saint Richard of Chichester
- King Henry I of Cyprus (born 1217)
- Amadeus IV of Savoy (born 1197)