Usk Castle is a castle site in the town of Usk in central Monmouthshire, South East Wales. Usk castle and town was probably laid out and established in 1120, after some of the other Norman settlements and castles of the region, such as Monmouth Castle and Abergavenny Castle. However, the site had a history of previous military, strategic, and local significance, for it was here that the Romans had established their early Legionary fortress before relocating it south to Caerleon.
Usk is first mentioned in 1138 in the context of it being captured by the Welsh. It passed back into Norman hands, only to be captured by the Welsh again in 1174, as was Abergavenny, when turmoil again developed into open conflict in this area of the Welsh Marches.