The River Honddu (Welsh: Afon Honddu) (pronounced hon-thee) is a river in the Black Mountains within the Brecon Beacons National Park, southeast Wales. Early recorded versions of the name are of the form Hothenei and hodni which are believed to contain the adjective 'hawdd' meaning for example, pleasant or easy. Later forms such as Honddye have undergone metathesis whereby -ddn- became -ndd-.