Eustace III was a notable figure in the 12th century, serving as the Count of Boulogne from 1150 until his death in 1183. He was the son of Eustace II and Mary of Scotland, and he played a significant role in the political landscape of medieval France and England. Eustace was known for his involvement in the Crusades and his support for the Plantagenet kings. Eustace III was married to Ida of Boulogne, and they had several children, including Eustace IV, who succeeded him as Count. His lineage and alliances through marriage helped strengthen the ties between the nobility of England and France. Eustace's legacy is marked by his contributions to the feudal system and the ongoing conflicts of his time.