Simon de Montfort, 6th Earl of Leicester

Simon de Montfort, 6th Earl of Leicester, 1st Earl of Chester, also known as Simon V de Montfort, was an English nobleman of French origin and a member of the English peerage, who led the baronial opposition to the rule of King Henry III, culminating in the Second Barons' War. Following his initial victories over royal forces, he became de facto ruler of England, and played a major role in the constitutional development of England.