Cefn-coed-y-cymmer (also Cefn coed y cymer, Cefn Coed y Cymer, Cefn Coed-y-cymmer and Cefncoedycymer) (]) is a small community on the northwestern edge of Merthyr Tydfil County Borough in Wales. It is situated in the neck of land between the rivers Taf Fawr and Taf Fechan at their confluence (Welsh: 'cymer'). The village lies within the community of Vaynor. Immediately to the north of the village is the hill of Cefn Cil Sanws on the southern slopes of which is Merthyr Tydfil Golf Club. The village is bounded both to the north and the west by the Brecon Beacons National Park.