The Cambrian Mountains are a mountain range in Mid Wales, reaching from the Brecon Beacons, North Carmarthenshire and Ceredigion in South Wales to Snowdonia in North Wales. Originally the term "Cambrian Mountains" was applied in a general sense to most of upland Wales. Since the 1950s, its application has become increasingly localised to the geographically homogeneous Mid Wales uplands of Plynlimon, Elenydd, and Mynydd Mallaen.
This barren and sparsely populated wilderness is known affectionately as the Desert of Wales.
The highest point of the range is Plynlimon. The area includes the source of the River Severn and River Wye, and has been proposed as a National Park. It is the type locality of the Cambrian period of the Paleozoic era (542-488Ma).
Cefn Croes, the site of a controversial wind farm project, is in the Cambrian Mountains, just south of the A44 road between Aberystwyth and Llangurig.