Kenilworth Castle is a castle in the town of Kenilworth in Warwickshire, England which was founded during the Norman conquest of England; with development through to the Tudor period. It has been described by the architectural historian Anthony Emery as "the finest surviving example of a semi-royal palace of the later middle ages, significant for its scale, form and quality of workmanship". Kenilworth played an important historical role: it was the subject of the six-month-long siege of Kenilworth in 1266, thought to be the longest siege in Medieval English history, and formed a base for Lancastrian operations in the Wars of the Roses. Kenilworth was the scene of the removal of Edward II from the English throne, the perceived French insult to Henry V in 1414 of a gift of tennis balls, and the Earl of Leicester's lavish reception of Elizabeth I in 1575. It has been described as "one of two major castles in Britain which may be classified as water-castles or lake-fortresses...".
The castle was built over several centuries. Founded in the 1120s around a powerful Norman great tower, the castle was significantly enlarged by King John at the beginning of the 13th century.