Thorney Island is an island that juts into Chichester Harbour in West Sussex. It is separated from the mainland by a narrow channel called the Great Deep.

Royal Air Force Thorney Island, or more simply RAF Thorney Island, is a former Royal Air Force station located on Thorney Island, West Sussex, England, 6.6 miles (10.6 km) west of Chichester and 7.1 miles (11.4 km) east of Portsmouth, Hampshire.