Gau Graig is a subsidiary summit of Cadair Idris in the Snowdonia National Park, in Gwynedd, northwest Wales.

It lies to the east of Mynydd Moel on a broad grassy plateau.

It marks the eastern end of the Cadair Idris ridge.

The summit is marked by a cairn.

To the north are Y Garn and Diffwys, to the west Rhobell Fawr and Aran Fawddwy and to the south are Waun-oer and Cribin Fawr.