Sgwd Henrhyd in Powys, Wales, is the tallest waterfall in South Wales with a drop of 90 feet (27 m). It lies on National Trust land on the southern edge of the Brecon Beacons National Park. The falls occur where the small river, the Nant Llech (grid reference SN854122) drops over the faulted edge of a hard sandstone known as the Farewell Rock. The nearest settlement to it is Coelbren, on the road between Glynneath and Abercraf. Though not in the core of the area, it is considered by many to constitute a part of South Wales' celebrated Waterfall Country.
The waterfall is reached after a steep walk down into the valley from the car park established by the National Trust, and is a popular spot to visit. One of the area's most famous visitors was Sir William Edmond Logan (later head of the Geological Survey of Canada), who carried out detailed geological survey work in the area, discovering near the foot of the falls the fossil trees which now stand outside Swansea Museum.