An area designated by English Nature to protect and conserve nationally important areas of wildlife habitat and geological formations and to promote scientific research. All National Nature Reserves are Sites of Special Scientific Interest.

areas defined by English Nature and considered to be of such national importance as to require preservation. Designated under Section 19 of the National Parks and Access to the Countryside Act 1949 or Section 35 of the Wildlife and Countryside Act 1981.

National Nature Reserves are areas of national and sometimes international importance for nature conservation which are owned or leased by English Nature or a body approved by them, or are managed in accordance with a Nature Reserve agreement with landowner and occupiers. Many such reserves are also SSSIs.