Arnulf III, Count of Flanders

Arnulf III (died 22 February 1071) was Count of Flanders from 1070 until his death at the Battle of Cassel in 1071. Biography Born , Arnulf was the eldest son of Count Baldwin VI of Flanders and Countess Richilde of Hainaut. On his deathbed in 1070, Baldwin left Flanders to his elder son, Arnulf, and Hainaut to the younger son, Baldwin, with the provision that if either preceded the other in death, he would inherit the other's county as well. Baldwin VI further entrusted his brother Robert with the safeguard of his son Arnulf, who was still a minor, to which Robert gave his oath of homage and solemn promise to protect his nephew.

After his father's death in 1070, his uncle Robert broke his oath and disputed the succession. Richilde appealed to King Philip I of France, who summoned Robert to appear before him. Robert refused and continued his aggression against Richilde and Arnulf, at which point Philip amassed an army which he brought to Flanders. The two forces met at the Battle of Cassel on 22 February 1071. but Robert himself was captured and his forces in turn captured the Countess Richilde. As a result of the battle Robert claimed the countship of Flanders. Richilde and her son Baldwin returned to Hainaut but continued to instigate hostilities against Robert. As he was a minor at his death and unmarried, Arnulf III had no issue.