Llyn Alwen is a small natural upland lake on Mynydd Hiraethog in Conwy County Borough, Wales at SH 898 565. It lies on the rolling Silurian moorland to the north-west of Mwdwl-eithin and about 10 km to the east of Betws y Coed. The discharge from the lake flows under the A543 road to form the headwater of Alwen Reservoir. The area was used as a special stage during the 2015 Wales Rally GB.

Llyn Alwen
Llyn Alwen
Location of the lake in Wales.
Location of the lake in Wales.
Llyn Alwen
LocationMynydd Hiraethog, Conwy County Borough, Wales
Coordinates53°05′41″N 3°38′51″W / 53.0947°N 3.6474°W / 53.0947; -3.6474
Typelake