Warwick Castle is a medieval shell keep type castle in Warwick, the county town of Warwickshire, England, sited on a cliff overlooking a bend in the River Avon. It is traditionally associated with the earldom of Warwick, one of the oldest in England, although it was not in their possession between the early 17th and mid-18th centuries.

Built by William I the Conqueror in 1068 to replace an Anglo-Saxon burh, Warwick Castle was used as a fortification until the early 17th century, when Sir Fulke Greville converted it to a country house. It was owned by the Greville family, who became earls of Warwick in the mid-18th century, until the 1970s. The castle was taken by Henry of Anjou, later Henry II, in 1153 when the Earl of Warwick's wife was tricked into handing over the castle, and was again lost temporarily in 1264, following a surprise attack during the Second Barons' War. It has been used to hold prisoners, including some from the Battle of Poitiers. Under the ownership of Richard Neville – also known as "Warwick the Kingmaker" – Warwick Castle was used in the 15th century to imprison the king, Edward IV. Warwick Castle has been compared with Windsor Castle in terms of scale, cost, and status; it demonstrated the power of the Earls of Warwick.

Since its construction in the 11th century, the castle has undergone various changes. Originally a wooden motte-and-bailey, it was rebuilt as a stone shell keep in 12th century. Repairs were necessary at various times due to slighting in battle and general decay. When Fulke Greville gained ownership of the castle in 1604 it was ruinous; £20,000 was spent on its restoration. In the 17th century the grounds were landscaped and turned into a garden. The castle was the subject of several paintings and drawings by the Italian master Antonio Canaletto. Warwick Castle was purchased by The Tussauds Group in 1978 and opened as a tourist attraction. It is protected as a Scheduled Ancient Monument and a Grade I listed building. The castle is a popular tourist attraction and features one of the world's largest siege engines. Warwick Castle is rumoured to be haunted; in 2006 it was featured in an episode of the television programme Most Haunted.