The War of the Sicilian Vespers or just War of the Vespers was a conflict that started with the insurrection of the Sicilian Vespers against Charles of Anjou in 1282 and ended in 1302 with the Peace of Caltabellotta. It was fought in Sicily, Catalonia (the Aragonese Crusade) and elsewhere in the western Mediterranean between the kings of Aragon on one side against the Angevin Charles of Anjou, his son Charles II, the kings of France, and the Papacy on the other side. The war resulted in the division of the old Kingdom of Sicily; at Caltabellotta, Charles II was confirmed as king of Sicily's peninsular territories ("Kingdom of Sicily on the other side of the Strait", that is, Naples), while Frederick III was confirmed as king of the island territories ("Kingdom of Sicily across the Strait", that is, Trinacria).

Peter III of Aragon (c. 1239 – November 1285) was King of Aragon, King of Valencia (as Peter I), and Count of Barcelona (as Peter II) from 1276 to his death. At the invitation of some rebels, he conquered the Kingdom of Sicily and became King of Sicily in 1282, pressing the claim of his wife, Constance II of Sicily, uniting the kingdom to the crown.