Eustace III, was a count of Boulogne, successor to his father.
He went on crusade in 1096 with his brothers Godfrey of Bouillon and Baldwin of Boulogne. When Godfrey died in 1100, Eustace was offered the kingship of Jerusalem, but declined the title. He died about 1125.
On his death the county of Boulogne came to his daughter, Matilda, and her husband Stephen, count of Blois, afterwards king of England, and in 1151 it was given to their son, Eustace IV.
