Lydney is a town and civil parish in the English county of Gloucestershire. It is on the west bank of the River Severn, in the Forest of Dean District, and is 16 miles (25 km) southwest of Gloucester as the crow flies. The town has been bypassed since 1995 by the A48 road. The population was about 8,960 in the 2001 census, reducing to 8,766 at the 2011 census.
Lydney has a harbour on the Severn, created when the Lydney Canal was built. Adjoining the town, Lydney Park gardens have a Roman temple dedicated to Nodens.