Merthyr Cynog is a hamlet and a community in the county of Powys in mid Wales. The population of the community at the 2011 Census was 245.
The Welsh name signifies the 'shrine of Cynog'. The grade II* listed church, a place of pilgrimage, is dedicated to Saint Cynog, a son of Brychan Brycheiniog. It is situated on the land between the valleys of the Ysgir Fawr and the Ysgir Fach which penetrate northwestwards into the uplands of Mynydd Epynt from the River Usk some miles to the south. The community includes the hamlet of Upper Chapel which lies a couple of miles to the northeast. To the north and west of Merthyr Cynog is the Army's extensive Sennybridge Training Area or 'SENTA'.
In 2013 Merthyr Cynog Community launched a new website.
Coordinates: 52°01′N 3°29′W / 52.017°N 3.483°W