River Neath (Welsh: Afon Nedd) is a river in south Wales running south west from its source in the Brecon Beacons National Park to its mouth at Baglan Bay below Briton Ferry on the east side of Swansea Bay.Several minor rivers rise on the southern slopes of Fforest Fawr. These include the Afon Hepste, Afon Sychryd, Afon Pyrddin, Nedd Fechan and Afon Mellte, the latter two converging at Pontneddfechan to form the River Neath.