Mynydd Carn-y-cefn (grid reference SO1808) is the name given to the broad ridge of high ground between the Ebbw Vale and the valley of the Ebbw Fach in the Valleys region of South Wales. It lies within the unitary area of Blaenau Gwent, formerly Monmouthshire.
The broad-topped ridge runs NNW-SSE and achieves a summit height of 550 metres (1,800 ft) at a point crowned by a trig point at OS grid ref SO 187084 between Ebbw Vale and Blaina. It is a Marilyn with a prominence of 176 metres.