:Devil's Appendix

{{Use dmy dates|date=April 2022}}

{{Infobox waterfall

| name = Devil's Appendix

| type = Plunge

| height = {{cvt|93|m|ft}}

| location = Snowdonia, Wales

| coords = {{coord|53.109835|N|4.035335|W |type:landmark_region:GB |display=inline,title}}

| watercourse = Afon Ogwen tributary

|native_name={{native name|cy|Nant Clogwyn y Geifr}}

}}

File:Cwm Idwal and Llyn Idwal.jpg

The Devil's Appendix ({{langx|cy|Nant Clogwyn y Geifr}}){{cite web |last1=Wyn |first1=Ieuan |title=Rhaid Gwarchod Enwau Lleoedd |date=24 June 2020 |url=https://ogwen.360.cymru/2020/rhaid-gwarchod-enwau-lleoedd/ |publisher=Ogwen360 |access-date=1 April 2021}} 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 {{convert|305|ft|m|abbr=off}} to reach the slopes above Llyn Idwal.Paul Williams, Rock Climbing in Snowdonia, Frances Lincoln, 2006 {{ISBN|0-7112-2408-0}} Depending on flow and the ambient temperature, it can be either an ice climbing route, a single drop waterfall, or a broken waterfall.{{cite web |title=Snowdonia |url=http://www.cavinguk.co.uk/holidays/Snowdonia2009/glyderau/ |work=CavingUK |accessdate=9 September 2009}}