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