Swiss anthropologist noted for his pioneering contributions to South American ethnohistory and the examination of African culture in Haiti.

Métraux studied with several prominent European anthropologists. He was director of the ethnological institute at the University of Tucumán, Arg. (1928–34), and wrote two classic works (1928) on the ethnohistory of the extinct Tupinambá Indians of Brazil. Following an expedition to Easter Island (1934–35), Métraux joined the Bishop Museum, Honolulu, and engaged in a major field effort in Argentina and Bolivia. In two works, Ethnology of Easter Island (1940) and L'Île de Pâques (1935; Easter Island), he argued that Easter Island's indigenous population is Polynesian, both culturally and physically, and that the island's well-known monolithic sculptures are native creations rather than Asian or American Indian ones.

As a member of the Bureau of American Ethnology of the Smithsonian Institution, Washington, D.C. (1941–45), Métraux contributed extensive, exemplary historical reconstructions to the bureau's Handbook of South American Indians (7 vol., 1946–59). From 1946 to 1962 Métraux held posts with the United Nations and the United Nations Educational, Scientific, and Cultural Organization (UNESCO). For the latter he engaged in studies in the Amazon (1947–48) and Haiti (1949–50). Le Vaudon haïtien (1958; Voodoo in Haiti), one of his two books on that island's culture, presented voodoo (Vodou) as a structured, complex religious system, examined its African origins, and showed its relation to Roman Catholicism in Haiti.