Derek Almey Ratcliffe (9 July 1929 – 23 May 2005) was one of the most significant British nature conservationists of the 20th century. He was Chief Scientist for the Nature Conservancy Council at the Monks Wood Experimental Station, Abbots Ripton, Huntingdon, retiring in 1989. Ratcliffe was the author of the 1977 Nature Conservation Review, a document which set out the most important sites for nature conservation in the United Kingdom. He also published various works on nature and conservation.