Llyn Gwynant lies on the River Glaslyn, in the Nant Gwynant valley, and is about 1¼ miles (2 km) north east of Llyn Dinas; the village of Bethania lies between them.
Snowdon lies 2 miles (3 km) to the north west. The lake is natural, having been formed by glacial action and is 120 acres (50 hectares) in size. It is a popular place for canoeing and kayaking with easy access from the A498 road which runs along its south bank.