| Devil's Appendix | |
| Type: | Plunge |
| Location: | Snowdonia, Wales |
| Coords: | 53.1098°N 4.0353°W |
| Watercourse: | Afon Ogwen tributary |
The Devil's Appendix (Welsh: Nant Clogwyn y Geifr)[1] is the tallest single-drop waterfall in Wales and one of the tallest in the United Kingdom. It is a plunge style waterfall located on the Clogwyn y Geifr cliffs beside Twll Du in Cwm Idwal, Snowdonia, Wales.
It is formed where a small stream falls for approximately 305feet to reach the slopes above Llyn Idwal.[2] Depending on flow and the ambient temperature, it can be either an ice climbing route, a single drop waterfall, or a broken waterfall.[3]