Alfonso IV, called the Kind (also the Gentle or the Nice, Catalan: Alfons el Benigne) was the King of Aragon and Count of Barcelona (as Alfonso III) from 1327 to his death. His reign saw the incorporation of the County of Urgell, Duchy of Athens, and Duchy of Neopatria into the Crown of Aragon.
Alfonso was born in Naples, the second son of James II and Blanche of Anjou. Alfonso became heir to the throne in December 1319 after his older brother James renounced his rights to become a monk. During the reign of his father, Alfonso was the procurator-general of the Crown, and in 1323-1324, he undertook the conquest of Sardinia. Alfonso's father and first wife Teresa died within a few days of each other in 1327. Teresa died in childbirth on 20 October 1327, and James II died on 2 November 1327, whereupon Alfonso became king.
Alfonso died in January 1336, aged only 36. He was succeeded by Peter IV, his 16-year-old son from his first marriage.
There are no Sardinian kings named Alfonso with numbers 1 to 3. The Sardinian royal title did not have a specific line of succession and all Aragonese kings used their own primary titles.