Llyn y Dywarchen is a small mountain lake of around 8 acres located above the village of Drws y Coed in Dyffryn Nantlle, near Rhyd-Ddu in Snowdonia.

Reached via the B4418 off the A4085 Beddgelert–Caernarfon road, the lake sits in an elevated, peaceful setting with views toward Snowdon and has been nominated as one of the 60 Wonders of Snowdonia.

It is also recognised as a notable stargazing spot within the national park. Access is straightforward, with a large lay-by providing limited parking for a handful of cars. A short walk through a gate in a stone wall brings visitors to the lakeshore.

The lake is primarily a fishing destination managed by the Seiont Gwyrfai and Llyfni Fishing Society, offering bank fishing and boats for wild brown trout and stocked rainbow trout.