William of Blois (c.1137-October 11, 1159) was Count of Boulogne (1153-1159) and Earl of Surrey (1153-1159). He was the second son of King Stephen of England and Matilda 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. The new King Henry was quite generous in his treatment of William of Blois, confirming his possession of the Earldom of Surrey jure uxoris (in right of his wife).

He married Isabella de Warenne, Countess of Surrey in her own right, in 1148. They had no children before his death in 1159. He was succeeded as Count of Boulogne by his sister Marie. His widow remarried to Hamelin Plantagenet.

Annals of Monte Fernando 1159: "Ob. Willelmus comes Bolonie."

Arms: Gules, three palets vair, on a chief or, an eagle displayed gules membered azure.