Langstone Harbour is a 2,085.4-hectare (5,153-acre) biological Site of Special Scientific Interest in Hampshire. It is an inlet of the English Channel in Hampshire, sandwiched between Portsea Island to the south and west, Hayling Island to the south and east, and Langstone to the north. It is part of the Ramsar site of Langstone and Chichester Harbour Special Protection Area and Nature Conservation Review site. Parts are Special Areas of Conservation, or Local Nature Reserves, and some areas by the Hampshire and Isle of Wight Wildlife Trust.

Hampshire is a ceremonial county in South East England. It is bordered by Berkshire to the north, Surrey and West Sussex to the east, the Isle of Wight across the Solent to the south, Dorset to the west, and Wiltshire to the north-west. The cities of Portsmouth and Southampton are the largest settlements and the county town is the city of Winchester.