The River Llynfi, otherwise referred to as the Llynfi River or Afon Llynfi in Welsh, is one of three main tributaries of the River Ogmore or Afon Ogwr. It runs for around 10 miles from its source north of Maesteg and flows generally southwards through the Llynfi Valley to the confluence with the River Ogmore (Afon Ogwr) and the River Garw at Aberkenfig (Abercynffig).