Grey Mare's Tail is a 60 metre hanging valley waterfall near to Moffat in southern Scotland. The fall is produced by the Tail Burn flowing from Loch Skeen cascading into the Moffat Water in the lower valley below. The surrounding area forms the Grey Mare's Tail Nature Reserve, owned by the National Trust for Scotland. The footpath from the valley floor up to Loch Skeen is one of the more popular walks in the area. Parking is also provided.