Cwm Clydach National Nature Reserve is a 24.8 hectares (61 acres) area of steeply sloping valley-side on Clydach Gorge, 2 miles (3.2 km) east of Brynmawr, southeast Wales.
It is protected for its ancient semi-natural beech woods, designated by the Nature Conservancy Council (now managed by its successor authority Natural Resources Wales).
[citation needed] The dense foliage of the beech canopy results in a rather minimal ground flora but species like bird's nest orchid are found amongst the leaf litter.
The high humidity of the more sheltered parts of the gorge encourage the growth of ferns, mosses and other lower plants including the lichen, Stricta sylvatica and the hay-scented buckler fern.
Birds of prey include sparrowhawk, kestrel and tawny owl.