Llynnau Mymbyr are two lakes located in Dyffryn Mymbyr, a valley running from the village of Capel Curig to the Pen-y-Gwryd hotel in Snowdonia, north-west Wales. The A4086 runs along their northern banks. Strictly speaking this is one lake, originally called Llyn Mymbyr, with a maximum depth of 30 feet. About 3/4 mile long in total, a delta has built up midway along the north shore, and this has to all purposes cut the lake in two - hence the plural name.