Crug Mawr is a hill in the Black Mountains in the Brecon Beacons National Park in southern Powys, Wales. Its summit at a height of 550m (1,805 ft) is marked by a trig point. The peak sits high above the valleys of the Grwyne Fawr and Grwyne Fechan to the north of the more well-known Sugar Loaf. The views from here across the Black Mountains are wide ranging and also extend eastwards across Monmouthshire.