In the year AD 1263...
- Following the unilateral annulment of the Provisions of Oxford two years prior by English king Henry III, the Barons' War breaks out in England between the king and leading noblemen, and would last until 1267. The war goes badly for the king in the opening months, as the charasmatic Simon de Montfort returns from self-imposed exile in France to lead the baronial forces in the capture of most of southeastern England, causing Henry to temporarily reinstate council government under the Provisions.
- Scottish king Alexander III defeats a combined Manx-Norse invasion force led by Manx king Magnus III and Norse king Haakon IV at the Battle of Largs, setting off a chain of events that would lead to Scottish domination of the Western Isles.
- Mamluk sultan Baibars besieges the Crusader holdout at Acre, but is unable to capture it. However, he does recapture the town of Nazareth, and has the Christian population massacred.
- Aragonese king James I reconquers Crevillente, Spain from the Moors.
- The last few holdout chieftans in the eastern part of Iceland submit to the authority of the Norse crown, bringing an end to the Icelandic Commonwealth and the Icelandic Civil War.
- Pope Urban IV concludes a secret treaty with Charles of Anjou, granting Charles the throne of Sicily. Charles would cement his claim three years later by defeating the actual ruler of Sicily, Manfred, in the Battle of Benevento.
- Genoa conquers the city of Chania on Crete from the Venetians.
- Hulegu Khan is defeated in an attempted invasion north of the Caucasus.
- Nahmanides, chief rabbi of Catalonia, defends the Talmud in a four-day disputation against apostate Pablo Christiani before King James I of Aragon and his court.
- The Roman Catholic synod at Arles condemns the doctrines of theologian Joachim of Fiore as heretical.
- The city of Sarajevo is founded, known at the time as "Vrh-Bosna."
- Oxford University's Balliol College is founded by John Balliol, father of the Scottish king with the same name.
- The "Savoy Palace" is constructed in London by Count Peter II of Savoy.
These people were born in the year 1263...
These people died in the year 1263...
- Grand Prince of Russia Alexander Nevsky, succeeded by his brother Yaroslav III.
- Norwegian king Haakon IV, due to wounds suffered in the Battle of Largs, succeeded by his son Magnus VI.
- Hojo Tokiyori, fifth regent of the Kamakura shogunate.
- Christian king of Lithuania Mindaugas, assassinated for his religious beliefes by his nephew Treniota, who returns the country to paganism.
- Manuel I, Emperor of Trebizond, succeeded by his son Andronicus II.
- Hugues Libergier, master of the works overseeing the construction of Rheims Cathedral, succeeded as master of the works by Robert de Coucy.
- Count Boniface of Savoy, succeeded by Peter II.
- Anglo-Norman nobleman Hamo de Crevequer, Lord Warden of the Cinque Ports.
- French cardinal Hugh of St. Cher.
1262 - 1263 - 1264