|Centuries:||12th century – 13th century – 14th century|
|Decades:||1230s 1240s 1250s – 1260s – 1270s 1280s 1290s|
|Years:||1259 1260 1261 – 1262 – 1263 1264 1265|
- King Mindaugas of Lithuania renounces Christianity, returning to his pagan roots and reverting to Grand Duke of Lithuania.
- The Icelandic Commonwealth enters into a treaty establishing a union with Norway and acknowledges Norwegian King Haakon IV as its ruler.
- Strasbourg becomes an Imperial Free City of the Holy Roman Empire.
- King Henry III of England obtains a papal bull releasing him from the Provisions of Oxford, preceding the Second Barons' War, a civil war started in 1263.
- King Mengrai of the Lannathai kingdom in present-day Thailand founds the city of Chiang Rai as the kingdom's first capital.
- Adam de la Halle writes the first operetta, "Le Jeu de la Feuillee".
- Richard of Chichester is canonized as a saint; he is best known for writing the prayer later adapted into the song Day by Day in the musical Godspell.
- July 15 – Richard de Clare, 6th Earl of Hertford, English soldier (born 1222)
- Aegidius of Assisi, companion of Saint Francis of Assisi
- Shinran Shonin, Japanese founder of the Jodo Shinshu branch of Pure Land Buddhism
- Matilda II of Boulogne, Queen of Portugal, spouse of King Afonso III of Portugal (born 1202)