Kaj Birket-Smith (20 January 1893 – 28 October 1977) was a Danish philologist and anthropologist. He specialized in studying the habits and language of the Inuit and Eyak. He was a member of Knud Rasmussen's 1921 Thule expedition. In 1940, he became director of the Ethnographic Department of the National Museum of Denmark.
Kaj Birket-Smith was the son of Danish librarian and literary historian Sophus Birket-Smith and wife, Ludovica (born Nielsen). He received his Ph.D. in linguistics at the University of Pennsylvania in 1937. He was a Knight of the Order of the Dannebrog.
In 1920, Kaj and Minna Birket-Smith wed. Kaj Birket-Smith died in 1977, aged 84.
- (1916). The Greenland bow. København: Bianco Lunos bogtr.
- (1918). A geographic study of the early history of the Algonquian Indians
- (1920). Ancient artefacts from the Eastern United States
- (1924). Ethnography of the Egedesminde District with Aspects of the General Culture of West Greenland
- (1925). Preliminary report of the Fifth Thule Expedition Physical anthropology, linguistics, and material culture
- (1928). On the origin of Eskimo culture
- (1928). Five hundred Eskimo words: A comparative vocabulary from Greenland and Central Eskimo dialects
- (1928). The Greenlanders of the present day
- (1928). Physiography of West Greenland
- (1929). The Caribou Eskimos. Material and social life and their cultural position
- (1929). Drinking-tube and tobacco pipe in North America
- (1930). Contributions to Chipewyan ethnology
- (1933). Geographical notes on the Barren
- (1938). The Eyak Indians of the Copper River Delta, Alaska
- (1940). Anthropological observations of the Central Eskimos
- (1943). The origin of maize cultivation