Llyn Geirionydd is situated above the village of Trefiw in the Conwy valley. It lies between the edge of the Gwydir forest and lower slopes of the Carneddau mountains.
It is the only lake in Snowdonia designated to permit power boats and water skiing.
Llyn Geirionydd runs parallel to Llyn Crafnant, separated by Mynydd Deulyn (mountain of the two lakes).
