Norwegian pioneer of modern oceanography whose studies of the physical structure and dynamics of the oceans were instrumental in transforming oceanography from a science that was mainly descriptive to one based on the principles of physics and chemistry.

Most of Helland-Hansen's work was done in Bergen, where he was successively director of the Marine Biological Station, professor at the Bergen Museum, and first director of the Geophysical Institute, which was established in 1917 largely through his efforts. He was active in international scientific affairs and in 1945 was elected president of the International Union of Geodesy and Geophysics.