Arnulf II of Flanders (960 or 961 – March 30, 988) was Count of Flanders from 965 until his death.

He was the son of Baldwin III of Flanders and Matilda of Saxony. Baldwin III died in 962, when Arnulf was just an infant, and with Arnulf's grandfather count Arnulf I of Flanders still alive. When Arnulf I died three years later (965), the regency was held by their kinsman Baldwin Balso.

By the time Arnulf attained his majority in 976, Flanders had lost some of the southern territory acquired by Arnulf I. The latter had given some parts of Picardy to King Lothar of France to help assure his grandson's succession, and gave Boulogne as a fief to another relative. Then early in Arnulf's minority Lothar had taken Ponthieu and given it to Hugh Capet, and the first counts of Guines had established themselves.

He married Rozala (Rosele) of Lombardy, daughter of Berengar II of Italy, and was succeeded by their son, Baldwin IV.