Stephen (1096 – October 25, 1154), the only King of England from the House of Blois, reigned from 1135 to 1154, when he was succeeded by his cousin Henry II, the first of the Angevin or Plantagenet Kings.
Stephen was born at Blois in France, the son of Stephen, Count of Blois, and Adela (daughter of William the Conqueror). His brothers were Count Theobald II of Champagne and Henry of
Blois, bishop of Winchester.
Stephen was sent to be reared at the English court of his uncle, King Henry I, in 1106. He became Count of Mortain in about 1115, and married Matilda, daughter of the Count of Boulogne, in about 1125, who shortly after became Countess of Boulogne. Stephen became joint ruler in 1128. In 1150 he ceased to co-rule, and in 1151, the County was given to his son, Eustace IV. When Eustace died childless, Stephen's next living son, William inherited the territory.