The siege of Kenilworth (21 June – December 1266), also known as the great siege of 1266, was a six-month siege of Kenilworth Castle and a battle of the Second Barons' War. The siege was a part of an English civil war fought from 1264 to 1267 by the forces of Simon de Montfort against the Royalist forces led by Prince Edward (later Edward I of England). The siege was one of few castle attacks to take place during the war.