Llyn Padarn is a glacially formed lake in Snowdonia, Wales, an example of a moraine dammed lake. The lake is approximately 2 miles long and linked to the neighbouring Llyn Peris (which forms the lower reservoir of the Dinorwig power station ). The town of Llanberis lies on the southern banks of the lake.
Padarn Country Park is located on the northern flank of the lake, including Coed Allt Wen, a rare and ancient oak woodland. Both the woodland and Llyn Padarn are designated as Sites of Special Scientific Interest.
The Llanberis Lake Railway also runs along its northern bank and various recreational activities take place on the lake, especially during the summer. These include canoeing, boating and fishing.