1262

1262 (MCCLXII) was a common year starting on Sunday of the Julian calendar, the 1262nd year of the Common Era (CE) and Anno Domini (AD) designations, the 262nd year of the 2nd millennium, the 62nd year of the 13th century, and the 3rd year of the 1260s decade. As of the start of 1262, the Gregorian calendar was 7 days ahead of the Julian calendar, which was the dominant calendar of the time.

• 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 2 – Arthur II, Duke of Brittany (died 1312)
• Ladislaus IV of Hungary (died 1290)
• Hugh le Despenser, 1st Earl of Winchester (died 1326)

• 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)