| Llyn Cefni | |
|---|---|
 The eastern side | |
  Llyn Cefni | |
| Location | Anglesey, Wales |
| Coordinates | 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 (1.4 mi) |
| Surface area | 86 ha (210 acres) |
| Water volume | 400 million imperial gallons (1.8 hm3; 1,500 acre⋅ft) |
Llyn Cefni is a small reservoir in the centre of Anglesey, Wales which is managed by Welsh Water and Hamdden Ltd, while the fishery is managed by the Cefni Angling Association.[1] The reservoir is located just 1 kilometre (0.6 mi) northwest of the island's county town of Llangefni.