List of Sites of Special Scientific Interest by Area of Search

The following is a list of Sites of Special Scientific Interest (SSSI) by area of search, in the United Kingdom. SSSIs are areas of conservation, consisting of protected areas, recognised for their biological or geological significance. In Northern Ireland an SSSI is called an area of special scientific interest (ASSI).
The English counties were revised under the 1974 reorganisation of local government. Until the 2010s, Natural England, which maintains the database of English SSSIs, kept the listing of counties as it was in 1974, but by 2015 they had updated their lists to reflect some later changes. However, two counties abolished in 1996 are still used as areas of search by Natural England, Avon (which is now divided between Somerset, Gloucestershire and Bristol) and Cleveland (which is now divided into County Durham and North Yorkshire).