Born at Naples, Alfonso was the eldest child of Ferdinand I of Naples by his first wife, Isabella of Clermont. She was the daughter of Tristan, Count of Copertino and Caterina Del Balzo Orsini. Alfonso was the cousin of Ferdinand II of Aragon, king of Aragon and the first (co-)ruler of a unified Spain. His teacher was the humanist Giovanni Pontano, whose De splendore describes the proper virtues and manner of life becoming to a prince.
When his mother Isabella of Clermont died (1465), he succeeded to her feudal claims, which included the Brienne claim to the Kingdom of Jerusalem.
In 1463, when Alfonso was fifteen, his great-uncle Giovanni Antonio del Balzo Orsini, Prince of Taranto, died, and he obtained some lands from the inheritance. Alfonso had shown himself a skilled and determined soldier, helping his father in the suppression of the Conspiracy of the Barons (1485) and in the defence of the Kingdom's territory against the Papal claims.
As a condottiero, he fought in the most important wars of the age, such the war following the Pazzi Conspiracy (1478–1480) and the War of Ferrara (1482–1484).
When his father died, the kingdom's finances were exhausted and the invasion of King Charles VIII of France was imminent; Charles (instigated by Lodovico Sforza, who wished to stir up trouble to allow him to seize power in Milan) had decided to reassert the Angevin claim to Naples and the accompanying title of King of Jerusalem.
Charles invaded Italy in September, 1494. Alfonso managed to regain the support of Pope Alexander VI, who invited Charles to devote his effort against the Turks instead. Alfonso received the official Papal coronation as Rex Siciliae on May 8, 1494 from Juan de Borja Lanzol de Romaní, el mayor, previously the papal legate to Alfonso II.
However, the King of France did not relent; by early 1495 Charles was approaching Naples, after having defeated Florence and the Neapolitan fleet under Alfonso's brother, Frederick of Calabria at Porto Venere. Alfonso, terrified by a series of portents, as well as unusual dreams (perhaps attributable to memories of his victims), abdicated in favour of his son, Ferdinand or Ferrandino, and fled, entering a Sicilian monastery. He died in Messina later that year. It had been 237 days since his coronation.
As Crown Prince, Alfonso had participated in the brilliant Renaissance culture that surrounded his father's court. His lasting contribution to European culture was the example set at his villas of La Duchesca and especially Poggio Reale just outside Naples, which so captivated Charles VIII of France during his brief sojourn at Naples during February–June 1495, that he was inspired to emulation of the "earthly paradise" he encountered.
Poggio Reale, which Vasari said was designed by Giuliano da Maiano and which was laid out in the 1480s, has utterly disappeared and no extensive description has survived. Decades later, Vasari reported, "At Poggio Reale [Giuliano da Maiano] laid out the architecture of that palazzo, always considered a most beautiful thing; and to fresco it he brought there Pietro del Donzello, a Florentine, and Polito his brother who was considered in that time a good master, who painted the whole palazzo, inside and out, with the history of the said king." There are no archives to connect Giuliano or his brother Benedetto with the project; for documentation only a section and plan, reproduced with apologies for its inaccuracy, by Sebastiano Serlio. Serlio's reproduction seems to show an idealized plan, identical on all four sides, ranged around a court with a double arcading.
It is clear that the Aragonese court at Naples introduced the Moorish garden traditions of Valencia, with its shaded avenues and baths, sophisticated hydraulics that powered splendid waterworks, formal tanks, fishponds and fountains, as a luxurious and secluded setting for court life, and combined them with Roman features: Alfonso's Poggio Reale was built around three sides of an arcaded courtyard with tiers of seating round a sunken centre that could be flooded for water spectacles; on the fourth side it opened onto a garden that framed a spectacular view of Vesuvius.
It was all unlike anything experienced by the French king, who retreated from Italy, loaded with tapestries and works of art, and filled with building and gardening ambitions.
Like his father, Alfonso married twice. His first wife was Ippolita Maria Sforza, whom he married on 10 October 1465 in Milan. His mistress, by whom he also had children, was Trogia Gazzela.
He had three children with Ippolita:King Ferdinand II of Naples (26 August 1469 – October 1496), married Joanna of Naples
Isabella of Aragon, Duchess of Bari and Princess of Bari (2 October 1470 – 11 February 1524), married her first cousin Gian Galeazzo Sforza, Duke of Milan, January 1490.
Piero, Prince of Rossano (31 March 1472 – 17 February 1491), Lieutenant General of Apulia, died of an infection following leg surgery.
And two with Trogia :Sancha of Aragon (born 1478 in Gaeta)
Alfonso, Duke of Bisceglie and Prince of Salerno (born 1481, in Naples)
Alfonso II of Naples is portrayed by Augustus Prew in the Showtime series The Borgias, although he is portrayed as much younger and flamboyant than his historical counterpart was in the 1490s. Sancha of Aragon is portrayed as his half-sister rather than his daughter. In Da Vinci's Demons he is played by Kieran Bew and is depicted as a sadistic warlord, bitterly jealous of Lorenzo the Magnificent.