Craig Rhiwarth is a mountain in the Berwyn range, in Powys (formerly Montgomeryshire), Wales, overlooking the village of Llangynog to the south.

On the summit is an Iron Age hillfort, and there are remains of slate quarrying on the southern slopes.

The altitude of Craig Rhiwarth is 532 metres (1,745 ft);[1] the hillfort is one of the highest in Wales.

[2][3] Within this area are the foundations of about 170 circular stone structures, of diameter 4–12 metres (13–39 ft).

There are also a few rectangular hafodydd, probably of medieval date, relating to seasonal settlement.