Caldicot Castle (Welsh: Castell Cil-y-coed) is an extensive stone medieval castle in the town of Caldicot, Monmouthshire, in southeast Wales, built near the site of Harold Godwinson's former Saxon castle by the Norman earls of Hereford from about 1100. The castle became a Grade I listed building on 10 June 1953.
It was in the possession of Thomas of Woodstock, a son of King Edward III of England, until his death in 1391, when it reverted to the Crown.
Caldicot is mentioned in the Domesday Book of 1086, not for its castle, but as an agricultural holding of Durand, Sheriff of Gloucester. Walter FitzRoger, Durand's nephew, inherited his lands as well as his father's office of Constable of England which remained with the lords of Caldicot. Walter's son Milo was granted the Earldom of Hereford to add to his titles. In the time of Henry I of England the castle was probably a simple motte-and-bailey.