Nant-y-Ffrith refers to a stream and the wooded valley through which it flows on the border between Flintshire and Wrexham County Borough in Wales.

The woodlands contain some deciduous trees but are dominated by recent conifer plantations planted by the Forestry Commission after the second world war.

They contain a range of flora and fauna including various ferns and mosses and woodland birds such as wood warbler and redstart.

During the 1950s, people travelled from miles around to park their cars on the Drofa (or hair-pin bend in English) overlooking Nant-y-Ffrith, and listen to nightingales, whose song echoed in the valley.

The closest high point across the valley in the village of Bwlchgwyn is the edge of a quarry where Fronheulog Hall once stood.

Roughly halfway down the gorge, approximately 100m upstream of a small wooden footbridge that crosses the stream, there is a large four-tier cascade waterfall hidden amongst the trees.

Access to the top of the falls is from a bend in the forestry track next to a sign warning of steep and dangerous ground.

Breeding birds on the reservoir include great crested grebe and coot with sedge warbler and reed bunting in the surrounding vegetation and lapwing and curlew in nearby fields.