Waldridge Fell is a Site of Special Scientific Interest located immediately south-west of Chester-le-Street in the northern part of County Durham, England.

[4] Also significant is that the Wanister Bog, an area of seasonally-flooded wetland on the south-east side of the fell, is the only valley-mire in lowland County Durham.

The principal species are sessile oak, Quercus petraea, birch, Betula pubescens and hazel, Corylus avellana, with alder, Alnus glutinosa, locally dominant along the watercourses and at spring-lines.

The understorey includes species such as wavy hair-grass, Deschampsia flexuosa, common bracken, Pteridium aquilinum, broad buckler fern, Dryopteris dilatata, and rowan, Sorbus aucuparia.

[11] Other notable insects include two other moths, northern drab, Orthosia opima, and dingy shell, Euchoeca nebulata, and a butterfly, the green hairstreak, Callophrys rubi.

[1] Another butterfly, the small pearl-bordered fritillary, Boloria selene, used to be common at Waldridge Fell but within County Durham is now confined to only four locations, all on heathland at around 300 metres above sea level.

[1] Rare plants that occur in Wanister Bog include devil's-bit scabious, Succisa pratensis, and marsh violet, Viola palustris.

[5] The last time Natural England surveyed the condition of Wanister Bog, it was losing water through a breach in the surrounding bund and, despite active management, the wetland was being invaded by Salix scrub and saplings.