Llanthony Priory is a partly ruined former Augustinian priory in the secluded Vale of Ewyas, a steep sided once glaciated valley within the Black Mountains area of the Brecon Beacons National Park in Monmouthshire, south east Wales. It lies seven miles north of Abergavenny on an old road to Hay on Wye at Llanthony. The main ruins are under the care of Cadw and entrance is free.