Eustace IV, Count of Boulogne

Eustace IV (c. 1129 – 17 August 1153), Count of Boulogne, was the eldest son of King Stephen of England and Countess Matilda I of Boulogne. When his father seized the English throne on Henry I's death in 1135, he became heir apparent to the English throne.

He was first mentioned in one of his parents' charters dated no later than August 1131. In 1137, he did homage for Normandy to Louis VII of France, whose sister, Constance, he subsequently married in 1140 (as a widow she remarried to Count Raymond V of Toulouse). Eustace was knighted in 1147, at which date he was probably from sixteen to eighteen years of age. In 1151 he joined Louis in an abortive raid upon Normandy, which had accepted the title of the Empress Matilda, and was now defended by her husband, Geoffrey of Anjou.

At a council held in London on 6 April 1152, Stephen induced a small number of barons to pay homage to Eustace as their future king; but the Archbishop of Canterbury, Theobald of Bec, and the other bishops declined to perform the coronation ceremony on the grounds that the Roman curia had declared against the claim of Eustace.

Eustace died suddenly the next year, in early August 1153, struck down (so it was said) by the wrath of God while plundering church lands near Bury St Edmunds. The death of Eustace was hailed with general satisfaction as opening the possibility of a peaceful settlement between Stephen and his rival, the young Henry of Anjou. According to William of Newburgh, King Stephen was "grieved beyond measure by the death of the son whom he hoped would succeed him; he pursued warlike preparations less vigorously, and listened more patiently than usual to the voices of those urging peace."

The Peterborough Chronicle, not content with voicing this sentiment, gives Eustace a bad character. "He was an evil man and did more harm than good wherever he went; he spoiled the lands and laid thereon heavy taxes." He had used threats against the recalcitrant bishops, and in the war against the Angevin party had demanded contributions from religious houses; these facts perhaps suffice to account for the verdict of the chronicler.

He was buried in Faversham Abbey in Kent, which was founded by his parents. They too were buried in Faversham Abbey; all three tombs are now lost, as a consequence of the Dissolution of the Monasteries.