Richard Lydekker (July 25, 1849 - April 16, 1915) was an English naturalist, geologist and writer of numerous books on natural history. He is also responsible for naming Aetosauria, a group of crurotarsans.
Lydekker was born in London, and educated at Trinity College, Cambridge, where he took a first-class in the Natural Science tripos (1872). In 1874, he joined the Geological Survey of India and made studies of the vertebrate paleontology of northern India (especially Kashmir). He was responsible for the cataloging of the fossil mammals, reptiles and birds in the Natural History Museum. His books included A Manual of Palaeontology (with Henry Alleyne Nicholson, 1889) and The Wild Animals of India, Burma, Malaya, and Tibet.
Lydekker was also influential in the science of biogeography. In 1895, he delineated the biogeographical boundary through Indonesia, known as Lydekker's Line, that separates Wallacea on the west from Australia-New Guinea on the east.
Lydekker wrote the Royal Natural History London, Frederick Warne, 1893-94 a six volume popular work.