Llyn Eigiau is a lake on the edge of the
Carneddau range of mountains in
Snowdonia,
Gwynedd, Wales. The name
Eigiau is thought to refer to the shoals of fish which once lived here. Early maps refer to it as
Llynyga. It is thought that a small number of
Arctic char exist in the lake (as they do in neighbouring
Llyn Cowlyd) after they were transferred here from
Llyn Peris, and certainly it is one of the few lakes in Wales to have its own natural
brown trout.