Adelolf, Count of Boulogne († 933), was a younger brother of Arnulf I, Count of Flanders and was given the County of Boulogne by his father. He was a son of Baldwin II, Count of Flanders, and of Ælfthryth, daughter of Alfred the Great. He was probably named for his maternal great-grandfather, King Æthelwulf of Wessex. Baldwin II's extensive lands and many offices in what is now the north of modern France and the west of Belgium were divided among his sons on his death in 918.