is a lake in the Carneddau range of mountains in Snowdonia, North Wales. It lies below the peaks of Pen yr Ole Wen and Carnedd Dafydd at a height of and covers an area of some .
The remains of two wartime aircraft, which crashed in 1942 and 1943, lie on the slopes round the lake.
Afon Lloer, its outflow, flows into Llyn Ogwen.