Usk, river in South Wales. The River Usk flows from its source high in the Brecon Beacons, rising in the Black Mountains, to its estuary in the Bristol Channel near the city of Newport. From the Brecon Beacons it flows north before turning sharply east through a valley and the town of Brecon. Following the line of the Welsh border, the river’s course continues south-east through Crickhowell and then turns south past Abergavenny before flowing by the towns of Usk and Caerleon. It is about 100 km (60 mi) long and is noted for its excellent fishing opportunities, particularly trout and salmon.

In 2002 the wreck of a 15th-century ship was discovered in Newport embedded in the banks of the River Usk. The legend of King Arthur is associated with the Usk, as the king’s court was said to have been situated at Caerleon overlooking the river.