The Avon Valley, also known as the Salisbury or Hampshire Avon is a river valley situated in central southern England. The river begins as two small rivers just north of Salisbury in the in the Vale of Pewsey. These smaller rivers merge flowing southwards across Salisbury Plain and through the town of Salisbury itself. At Salisbury, the Avon is joined by three of its major tributaries - the Rivers Bourne, Nadder and Wylye, and a short distance downstream by the River Ebble. After which it enters Hampshire, flowing alongside the lowland heath of the New Forest National Park and down through Ringwood to Christchurch where it merges with the River Stour and flows into Christchurch Harbour. The overall catchment area is about 1,750 square kilometres, made up of steep sided chalk valley in the north and extensive open wet grassland in the south.
The Avon and associated wetlands support habitats and species of national and international importance, with Sites of Special Scientific Interest (SSSI), Special Area of Conservation, Special Protection Area and Ramsar designations. In recent years populations of breeding waders have undergone significant declines.