Peter III (Peter the Great), 1239?–1285, king of Aragón and count of Barcelona (1276–85) and king of Sicily (1282–85); son and successor of James I. In 1280 he established Aragonese influence on the northern shores of Africa. From his marriage (1262) to Constance, daughter and heir of Manfred of Sicily, were derived the claims of the house of Aragón to Sicily and S Italy. After the insurrection of the Sicilian Vespers against Charles I of Anjou, Peter was offered the crown of Sicily and took possession of the island (1282). Pope Martin IV excommunicated him and declared him deprived of his states on the basis of Peter II's declaration of vassalage to the Holy See. A crusade against Aragón was organized by the pope and the French, who invaded Catalonia but were repulsed by Peter and defeated at sea by Roger of Loria. Peter's Sicilian venture was unpopular with the Aragonese nobility and towns, and he was compelled to grant them wide privileges to quell their opposition. He founded the first university in Aragón at Huesca. Peter was succeeded in Aragón by his eldest son, Alfonso III, and in Sicily by his second son, James (later James II of Aragón).
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