Llyn Cefni

Llyn Cefni
The eastern side
Location	Anglesey, Wales
Coordinates	53°16′16″N 4°20′8″W / 53.27111°N 4.33556°WCoordinates: 53°16′16″N 4°20′8″W / 53.27111°N 4.33556°W
Type	Reservoir
Primary outflows	Afon Cefni
Basin countries	United Kingdom
Max. length	2.3 km
Surface area	0.86 km²
Water volume	400 million gallons

Llyn Cefni is a small reservoir in the centre of Anglesey, Wales which is managed by Welsh Water and Hamdden Ltd. It is located just one kilometre northwest of the island's county town of Llangefni and is the source of the Afon Cefni and other smaller watercourses. The reservoir and the immediate surrounding area have been designated as a nature reserve, and as a further measure of conservation an artificial plantation of trees runs along its north shore. The tracks of the Anglesey Central Railway, although no longer used, still run over an embankment which crosses the water. The reservoir is easily accessible from Llangefni, as well defined paths run from the town through the local nature reserve, The Dingle.

At the maximum length of 2.3 kilometres and a total water surface area of 0.86 km² it is the second largest body of water on the island after Llyn Alaw, also a reservoir. There is also a dam on the south-east edge of the reservoir, next to which is a car park.