William de Mandeville

William de Mandeville was the name of two important barons in medieval England, all of the same family.

William de Mandeville (d. sometime between 1105 and 1116) inherited the estates of his father Geoffrey around 1100. He was constable of the Tower of London at that time, and thus keeper of the first person known to be imprisoned there for political reasons, Ranulf Flambard. Flambard's February 1101 escape would have significant consequences for William.

It is not known if William was in some way a confederate of Flambard, or was simply a lax guardian. Either way, king Henry I apparently took away the heart of William's Essex estates. Little is known of William's activities after this.

William probably married Margaret, daughter of Eudo Dapifer and Rohese de Clare. Their son Geoffrey would recover the seized estates, and gain much else besides.

William de Mandeville, 3rd Earl of Essex (d. 1189) was a close councilor of Henry II. He was the son of Geoffrey de Mandeville, 1st Earl of Essex and grandson of the William de Mandeville above.