Grosmont Castle is a ruined castle in Grosmont, Monmouthshire, Wales, very near the border with Herefordshire, England, and overlooking a bend in the River Monnow. It is generally considered to have been largely built by Hubert de Burgh early in the 13th century, on an earlier Norman foundation, but was extended in the 14th century. It is located about 11mi north-east of Abergavenny, 11mi north-west of Monmouth, and 15mi south-west of Hereford. The castle ruins have been Grade I listed since 1 September 1956.