William II, Duke of Apulia

William II (1095 – July 1127) was the Duke of Apulia and Calabria from 1111 to 1127. He was the son and successor of Roger Borsa. His mother, Adela of Flanders, had previously been queen of Denmark, and he was a half-brother of Charles the Good.

He succeeded his father as duke in 1111, though Adela served as regent until William was of age. Like father, like son: he proved utterly inept at governing his Italian possessions. He could not avoid conflict with his cousin Roger II of Sicily, and in 1121 Pope Calixtus II personally intervened to make peace between the warring cousins. William and Roger came to an agreement, whereby Roger provided knights to help William quash a revolt of the minor baron Jordan of Ariano, and in exchange, William abandoned his Sicilian and Calabrian lands.

In 1114, William married a daughter of Count Robert of Carazzo, but they had no children. He died without legitimate posterity in July 1127, leaving the entire of the Norman Mezzogiorno to his first cousin once removed, Roger of Sicily, his erstwhile ally.

Generally considered an insignificant ruler by modern historians, William was respected by his contemporaries, popular with his barons and subjects, and praised for his martial prowess.