Eustace IV, Count of Boulogne

Eustace IV was the eldest son of King Stephen of England and Countess Matilda I of Boulogne. He became the Count of Boulogne in 1146, following his mother's death. As heir apparent to the English throne, he did homage for Normandy to King Louis VII of France in 1137 and married Louis's sister Constance in 1140.

During the Anarchy, Eustace was involved in military actions, including a raid on Normandy in 1151 with his brother-in-law Louis VII. In 1152, his father attempted to secure his succession by having barons pay homage to him, but the church refused to crown him. This led to tensions with the clergy, and Eustace was reportedly involved in coercive actions against them.

Eustace IV died suddenly in mid-August 1153, reportedly while plundering church lands near Bury St Edmunds. He was buried in Faversham Abbey, Kent. After his death, the Treaty of Winchester established Henry Plantagenet as Stephen's heir.