The Afon Lwyd or Afon Llwyd (English: 'grey river') is a 13-mile (21 km) long river in south-east Wales which flows from its source northwest of Blaenavon, through Abersychan, Pontnewynydd, Pontypool, Llanfrechfa and Cwmbran before flowing, at Caerleon, into the River Usk, which subsequently flows into the Bristol Channel to the south of Newport.