Danish- Eskimo explorer and ethnologist who, in the course of completing the longest dog-sledge journey to that time, across the American Arctic, made a scientific study of virtually every Eskimo tribe in that vast region.

Partly of Eskimo descent himself, and equipped with a thorough mastery of the Eskimo language, Rasmussen wintered among the most northerly tribe in the world, the Polar Eskimo of northwestern Greenland (1902–04). He studied the possibility of introducing reindeer husbandry to western Greenland (1905), spent the next two years again among the Polar Eskimo, and founded a permanent station at Thule, Greenland, in 1910. Its purpose was to provide a trading centre for the population and a base for expeditions. With three companions he crossed the Greenland Ice Sheet, in 1912, from Thule to the northeast coast. His expedition of 1916–18 surveyed the north coast of Greenland. In 1919 he went to Angmagssalik in eastern Greenland to collect Eskimo tales.

On Sept. 7, 1921, at Upernavik, he began the great expedition during which he planned to visit every Eskimo tribe from Greenland to the Bering Strait. After investigations in northeastern Canada, on March 4, 1923, he set off on his trek across the continent and reached Point Barrow, Alaska, on May 23, 1924. Along the way he traced Eskimo migration routes and observed the basic unity of Eskimo cultures. He described this expedition in Across Arctic America (1927).

On subsequent expeditions from Thule, Rasmussen made cartographic, archaeological, and ethnographical studies in southeastern Greenland. His rich literary production includes travel descriptions and translations of Eskimo mythology and songs as well as scientific works, such as Grønland, Langs Polhavet (1919; Greenland by the Polar Sea).