The River Clydach or Afon Clydach is a river in the county borough of Neath Port Talbot, Wales. It runs generally southwards from the western slopes of Mynydd Marchywel for about 9 km and past Fforest Goch, Bryncoch and Neath Abbey to join the River Neath near Neath.[1] Each of the rivers bearing the name 'Clydach' in South Wales is thought to derive from an earlier Celtic word 'klou' or 'kleu' together with the suffix '-ach' which is of Irish origin. The sense is of a 'strong-flowing', 'washing' or stony river.[2]