William II (December 115311 November 1189), called the Good, was king of Sicily from 1166 to 1189. From surviving sources William's character is indistinct. Lacking in military enterprise, secluded and pleasure-loving, he seldom emerged from his palace life at Palermo. Yet his reign is marked by an ambitious foreign policy and a vigorous diplomacy. Champion of the papacy and in secret league with the Lombard cities, he was able to defy the common enemy, Frederick Barbarossa. Recent scholarship has also stressed that the relative stability of William's reign on the mainland rested less on the disappearance of aristocratic power than on a continuing political settlement in which counts, lesser barons, and royal military officers remained central to the governance of Apulia and the Terra di Lavoro. In the Divine Comedy, Dante places William II in Paradise. He is also referred to in Boccaccio's Decameron (tale IV.4, where he reportedly has two children, and tale V.7).
William was nicknamed "the Good" only in the decades following his death. It is due less to his character than to the cessation of the internal troubles that plagued his father's reign and the wars that erupted under his successor. Under the Staufer dynasty his reign was characterised as a golden age of peace and justice. His numeral is contemporary and he himself used it.
Kingship
Regency of his mother
William was born in Palermo to William I and Margaret of Navarre. At the age of twelve his father died, and he was placed under the regency of his mother. In 1171 he was declared adult and until then the government was controlled first by the chancellor Stephen du Perche (1166–1168), cousin of Margaret, and then by Walter Ophamil, archbishop of Palermo, and Matthew of Ajello, the vice-chancellor.
Marriage and alliances
An effort by Bertrand II, archbishop of Trani, to negotiate the hand of Byzantine Princess Maria for William yielded no fruit and led to his breaking up with Byzantine Emperor Manuel I Comnenus in 1172. In 1173, the Emperor Frederick Barbarossa proposed William's marriage with his daughter, Beatrice, but William refused to offend the pope.
In the same year the death of Henry, Prince of Capua marked a potential succession crisis: it was said that William II had Constance, the last legitimate heir to the throne, appointed heir and sworn fealty in 1174, but she remained confined in her monastery. By this stage, the succession question had implications not only for the royal household but also for the balance of power across the mainland provinces, where counties, lordships, and offices remained politically consequential prizes.
In 1174 and 1175 William made treaties with Genoa and Venice and his marriage in February 1177 with Joan, daughter of King Henry II of England and Duchess Eleanor of Aquitaine, marks his high position in European politics. This step, of great consequence to the Norman realm, was possibly taken that William might devote himself to foreign conquests,
thumb|left|[[Monreale Cathedral, built during William's II reign. William and his parents are buried there.]]
Wars with Egypt and Byzantine Empire
Unable to revive the African dominion, William directed his attack on Ayyubid Egypt, from which Saladin threatened the Latin kingdom of Jerusalem. In July 1174, 30,000 men were landed before Alexandria, but Saladin's arrival forced the Sicilians to re-embark in disorder. A better prospect opened in the confusion in Byzantine affairs which followed the death of Manuel Comnenus (1180), and William took up the old design and feud against the Byzantine Empire.