Carnedd Dafydd is a mountain peak in the Carneddau range in Snowdonia, Wales, and is the third highest peak in Wales, or the fourth if Crib y Ddysgl on the Snowdon ridge is counted. Situated south-west of Carnedd Llewelyn and north of Pen yr Ole Wen, Carnedd Dafydd is on the main ridge of the Carneddau, and on the border between Gwynedd and Conwy. The average annual temperature of the mountain is around 3–4 °C (37–39 °F).