Lydney is a town and civil parish in Gloucestershire, England. 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. The town has been bypassed by the A48 road since 1995. The population was about 8,960 in the 2001 census, reducing to 8,766 at the 2011 census. Increasing to 10,043 at the 2021 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.