Attributed arms of William I, Count of Boulogne (pre-heraldic era)
|Count of Boulogne|
|Reign||17 August 1153 – 11 October 1159|
|Died||11 October 1159 (aged c. 22)|
|Spouse||Isabel de Warenne, 4th Countess of Surrey|
|Father||Stephen, King of England|
|Mother||Matilda I, Countess of Boulogne|
William I of Blois (c. 1137 – 11 October 1159) was Count of Boulogne (1153-1159) and Earl of Surrey jure uxoris (1153-1159). He was the second son of King Stephen of England and Countess Matilda I of Boulogne.
When his elder brother, Eustace IV of Boulogne, died in 1153, William was passed over in the succession to England. His father instead conceded the throne to the young Henry Plantagenet (son of his cousin, Matilda), in order to end the war between Stephen and Henry, of which both sides were growing weary. The new King Henry initially allowed William of Blois to retain the earldom of Surrey jure uxoris (in right of his wife).
However, Gervase of Canterbury asserts a plot against Henry's life was discovered in 1154 among some Flemish mercenaries. The plan was to assassinate Henry in Canterbury, and allegedly William of Blois had knowledge of this plot or was in connivance with the mercenaries. Whatever the truth, Henry fled Canterbury and returned to Normandy.
William of Blois had married Isabel de Warenne, 4th Countess of Surrey, in 1148. They had no children. He died, in 1159, of disease near Toulouse, and was buried at the Poitevin abbey of Montmorel. He was succeeded as Count of Boulogne by his sister, Mary I. His widow remarried to Hamelin Plantagenet.
|Ancestors of William I, Count of Boulogne|
| Count of Boulogne
| Count of Mortain|