Cefn Hirgoed is a ridge in Bridgend county borough in South Wales. The ridge extends for about 5 km east from the village of Sarn just north of Bridgend to Pen-prysg north of Pencoed. At the point where it reaches its highest elevation of 142m, are a couple of covered reservoirs. Towards the west the M4 motorway runs along the hill’s southern edge.

The hill is formed from relatively hard-wearing sandstones of the South Wales Lower Coal Measures with mudstone layers between the sandstones which here dip steeply northwards into the South Wales Coalfield syncline.

Almost the entire hill is mapped as open country under the Countryside and Rights of Way Act 2000 giving a general right of access on foot to the public. It and the adjacent Hirwaun Common are also crossed by several public footpaths. A couple of minor roads, Heol Spencer and Heol Llan/Heol-Las, run north-south across the ridge.

Early records refer to Robert Thomas who is 1661 was charged at the Great Sessions of Glamorgan with the murder of Edmund Thomas in a duel fought on Cefn Hirgoed on the 4th February 1660.

He was outlawed and his lands and possessions taken from him. In 1669 he was pardoned with a restitution of lands and possessions, including Tregroes House in Pencoed.

• images of Cefn Hirgoed and area on Geograph website