He made his first trip to the Arctic on a sealer in 1882 and upon his return became curator of the natural history collection of the Bergen Museum. In 1888, with a party of five, he made a memorable journey across Greenland on skis, described in his First Crossing of Greenland (1890).
Conceiving a startling and much-derided plan for reaching the North Pole by drifting in the ice across the polar basin, he sailed to the Arctic in 1893 in the Fram, especially designed to resist crushing by ice. The Fram was anchored in the ice pack at lat. 83°59−N, drifted northward to 85°57−, and later (1896) returned safely (although without having reached the pole) to Norway, as Nansen had predicted, by way of Spitsbergen. In the meantime, Nansen had left the ship in 1895 and with F. H. Johansen set forth to complete the journey to the pole by sledge. They were, however, turned back by ice conditions at lat. 86°14−N, the northernmost point to have been reached at that time.
When they were wintering (1895–96) on Franz Josef Land (now often called Fridtjof Nansen Land), members of the Jackson-Harmsworth expedition (see Jackson, Frederick George) chanced upon them and sent them home in one of their ships. Nansen's arrival in Norway was followed eight days later by that of the Fram, under Otto Sverdrup. Although neither he nor his ship had reached the North Pole, his expedition gave the world much new valuable information about the Arctic Ocean and the Arctic and made Nansen internationally famous. He had proved that a frozen sea lay around the Pole and filled the polar basin (see Arctic Ocean).
With his highly detailed information on oceanography, meteorology, diet, and nutrition, Nansen had laid the basis for all future arctic work. Farthest North, his account of this brilliant exploit, appeared in English translation in 1897, and the expedition's scientific material was published as The Norwegian North Polar Expedition (ed. by Nansen, 6 vol., 1900–1906). The Nansen Fund for scientific research was established in his honor. At the university in Christiania (now Oslo), he became professor of zoology (1897) and of oceanography (1908).