Thomas Fredrik Weybye Barth (born 1928) is a Norwegian social anthropologist who has published several ethnographic books with a clear formalistic view. He is professor in the Department of Anthropology at Boston University, and has previously held professorships at the University of Oslo, the University of Bergen (where he founded the Department of Social Anthropology), Emory University and Harvard University.

He is well-known among anthropologists for his transactional analysis of politic processes in the Swat Valley of northern Pakistan and his study of microeconomic processes and entepreneurship in the area of Darfur in Sudan. The latter has been regarded as a classical example of formalistic analysis in economic anthropology. During his long career he has also done acclaimed studies based on field works in Bali, New Guinea, and several countries in the Middle East, thematically covering a wide array of subjects.

Barth was the editor of Ethnic Groups and Boundaries (1969) in which he outlines an approach to the study of ethnicity which focuses on the on-going negotiations of boundaries between groups of people. Barth's view is that such groups are not discontinuous cultural isolates, or logical a prioris to which people naturally belong.

Barth wants to part with anthropological notions of cultures as bounded entities, and ethnicity as primordialist bonds, replacing it with a focus on the interface between groups.
Ethnic Groups and Boundaries, therefore, is a focus on the interconnectedness of ethnic identities. Barth writes (p. 9): "[...] categorical ethnic distinctions do not depend on an absence of mobility, contact and information, but do entail social processes of exclusion and incorporation whereby discrete categories are maintained despite changing participation and membership in the course of individual life histories." Furthermore, Barth accentuates that group categories - i.e. ethnic labels - will most often endure even when individual members move across boundaries or share an identity with people in more than one group.

The interdependency of ethnic groups is a pivotal argument throughout both the introduction and the following chapters in Barth's edited book. As interdependent, ethnic identities are the product of continuous so-called ascriptions and self-ascriptions, whereby Barth stresses the interactional perspective of social anthropology on the level of the persons involved instead of on a socio-structural level. Ethnic identity becomes and is maintained through relational processes of inclusion and exclusion.

Barth is married to Unni Wikan, professor of social anthropology at the University of Oslo, Norway. He is the son of professor of geology Tom Barth and newphew of professor of zoology Edvard Kaurin Barth.

Selected bibliography

• Balinese worlds. Chicago: University of Chicago Press, 1993. ISBN 0226038335

• Cosmologies in the making : a generative approach to cultural variation in inner New Guinea. Cambridge: Cambridge University Press, 1987. ISBN 0521342791

• Sohar, culture and society in an Omani town. Baltimore: Johns Hopkins University Press, 1983. ISBN 0801828406

• Ritual and knowledge among the Baktaman of New Guinea. Oslo: Universitetsforlaget, 1975. ISBN 0300018169

• Ethnic groups and boundaries. The social organization of culture difference. Oslo: Universitetsforlaget, 1969. ISBN 9780045720194

• Models of social organization. London, Royal Anthropological Institute, 1966.

• Nomads of South-Persia; the Basseri tribe of the Khamseh Confederacy. Oslo: Universitetsforlaget, 1962.

• Political leadership among Swat Pathans. London : The Athlone Press, 1959.