The Long Mountain (Welsh: Cefn Digoll) is a hill to the east of Welshpool in Powys, Wales. It rises to a height of 408m at Beacon Ring, where there is a hill fort.
The Long Mountain extends from Forden in the southwest to Vennington in Shropshire to the northeast. It is sometimes considered to include the Breidden Hills.
There was a Roman road along the Long Mountain, part of a route from Uriconium (Wroxeter) to Lavobrinta (Forden Gaer)[1]. At the southern end of the hill there are traces of Offa's Dyke, and the Offa's Dyke Path traverses the hill.
In 630 the hill was the scene of the Battle of Cefn Digoll, between Northumbria and an alliance of Gwynedd and Mercia.
The Long Mountain is a Marilyn.