Myarth is a hill in the Usk Valley in the county of Powys in South Wales, about 2 miles west of Crickhowell.

Its summit at 292 metres (958 ft) is covered by trees, whilst the larger part of its slopes are also wooded.

Myarth has an elongate form commonly ascribed to erosion by the west-to-east movement of the Usk Valley glacier during successive ice ages.

The River Usk runs along the foot of the hill on its southern side.

[1] In 2016, the hill was used as the location for a segment of an episode of the motoring series The Grand Tour.