Henry III (1 October 1207 – 16 November 1272) is the son and successor of John (Jean sans Terres) as King of England, reigning for 56 years from 1216 until his death.

His contemporaries know him as Henry of Winchester.

He is the first child king in England since the reign of Æthelred the Unready.

England prospers during his reign and his greatest monument is Westminster, which he makes the seat of his government and where he expands the abbey as a shrine to Edward the Confessor.

He is the first of only five monarchs to reign in the Kingdom of England or its successor states for 50 years or more, the others being Edward III (1327–1377), George III (1760–1820), Victoria (1837–1901) and Elizabeth II (1952–present).

He assumes the crown under the regency of the popular William Marshal, 1st Earl of Pembroke, but the England he inherits had undergone several drastic changes in the reign of his father.

He spends much of his reign fighting the barons over Magna Carta and the royal rights, and is imprisoned by rebel leader Simon de Montfort, leader of the baronial cause.

Under de Montfort's leadership, and against Henry's will, England's first Parliament is called.

His son Edward, aided by ally Roger Mortimer, will eventually defeat de Montfort and reassert royal power.

Henry is also unsuccessful on the Continent, where he endeavors to reestablish English control over Normandy, Anjou, and Aquitaine.