Chichester Harbour is a large natural harbour in West Sussex and Hampshire. It is situated to the south-west of the city of Chichester and to the north of the Solent. The harbour and surrounding land has been designated as an Area of Outstanding Natural Beauty (AONB) and a biological and geological Site of Special Scientific Interest (SSSI). The area is also part of the Solent Maritime Special Area of Conservation, Chichester and Langstone Harbours Ramsar site, Special Protection Area and Nature Conservation Review site, Grade I. Part of it is a Geological Conservation Review site and two areas are Local Nature Reserves.
Five institutional landowners that own land or foreshore within Chichester Harbour SSSI include the Crown Estate, the Church Commissioners, the Ministry of Defence (around Thorney island), the National Trust (East Head) and the Royal Society for the Protection of Birds (Pilsey Island).