The Naturalist on the River Amazons, subtitled A Record of the Adventures, Habits of Animals, Sketches of Brazilian and Indian Life, and Aspects of Nature under the Equator, during Eleven Years of Travel, is an 1863 book by the British naturalist Henry Walter Bates about his expedition to the Amazon basin. Bates and his friend Alfred Russel Wallace set out to obtain new species and new evidence for evolution by natural selection, as well as exotic specimens to sell. He explored thousands of miles of the Amazon and its tributaries, and collected over 14,000 species, of which 8,000 were new to science. His observations of the coloration of butterflies led him to discover Batesian mimicry.

Henry Walter Bates was an English naturalist and explorer who gave the first scientific account of mimicry in animals. He was most famous for his expedition to the rainforests of the Amazon with Alfred Russel Wallace, starting in 1848. Wallace returned in 1852, but lost his collection on the return voyage when his ship caught fire. When Bates arrived home in 1859 after a full eleven years, he had sent back over 14,712 species of which 8,000 were new to science. Bates wrote up his findings in his best-known work, The Naturalist on the River Amazons.