English medical psychologist and anthropologist known principally for The Todas (1906), a model of precise documentation of a people, and the important History of Melanesian Society, 2 vol. (1914).

After training as a physician, Rivers conducted research on problems of physiological psychology. In 1897 he became director of Britain's first experimental psychology laboratory (University of London), and in the same year he was appointed lecturer at the University of Cambridge, where he was pivotal in instituting the study of experimental psychology. In 1898 he joined the Cambridge expedition to the Torres Strait (between New Guinea and Australia), administered tests of sensory functions to Melanesians, and became keenly interested in anthropological fieldwork. He became a fellow of St. John's College, Cambridge, in 1902. Shortly afterward he made a firsthand study of the Toda people of southern India and later paid several visits to Melanesia. His ideas on kinship terminology were advanced in Kinship and Social Organisation (1914). Rivers devoted the rest of his life to medical psychology. His Instinct and the Unconscious (1920) did much to encourage a sympathetic British attitude toward psychoanalytic theory.