The Nedd Fechan or 'Little Neath' is a river in the county of Powys, south Wales, Great Britain. It rises on the eastern slopes of Fan Gyhirych in the Fforest Fawr section of the Brecon Beacons National Park and flows south for 12 km / 7 mi to join with the Afon Mellte at Pontneddfechan, their combined waters continuing as the River Neath (Welsh Afon Nedd) to the sea near Swansea.