- Category: Water Feature
- Type: Inland Water
- Latitude/Longitude: 52°55'27"N 4°11'31"W
- Eastings/Northings: 252743, 338559
- OS Grid: SH527385
- Mapcode Local: GBR 5M.MVK0
- Mapcode Global: WH55K.LR1L
Location and coordinates are for the approximate centre of Llyn Ystumllyn within this administrative area.
Geographic features and populated places may cross administrative borders.