Richard Rathbun was born on January 25, 1852, in Buffalo, Erie County, New York.

He was an American naturalist. While attending Cornell University, he became an assistant in zoology at the Boston Society of Natural History in 1873. In 1874 and 1875, he spent the summer assisting the U.S. Fish Commission, a division of the Smithsonian Institution. He was appointed the official geologist of an expedition to Brazil to investigate its natural resources. In 1876, he was appointed scientific assistant in the U.S. Fish Commission, a position he held for eighteen years. In 1880, he became curator of marine invertebrates at the Smithsonian Institute in Washington, D.C. In 1896, he was made assistant secretary, and in 1898, the director of the Smithsonian. In 1902, he became president of the Washington Philosophical Society, and in 1905, president of the Cosmos Club. He was also a Fellow of the American Association for the Advancement of Science and a member of the Fisheries Society of Finland, the Russian Imperial Society for the Acclimatization of Animals and Plants, the Zoological Society of London, the International Zoological Congress, the International Congress of Applied Chemistry, the Pan American Scientific Congress, and others. He was granted honorary degrees by the University of Indiana, Bowdoin College, Pittsburgh University, and George Washington University. Rathbun was instrumental in the establishment of the natural history building of the Smithsonian Institution.

In 1880, he married Carolyn (Lena) Augusta Hume (1851–1922). He died on July 16, 1918, in Washington, D.C.