Lloyd Viel Berkner (born February 1, 1905, in Milwaukee, died June 4, 1967, in Washington, D.C.) was the U.S. physicist and engineer who first measured the height and density of the ionosphere. This permitted the first complete theory of short wave radio propagation.

Later he investigated the development of the Earth's atmosphere. Since he needed data from the whole world, he proposed the International Geophysical Year in 1950. At that time, the IGY was the largest cooperative study of the Earth ever undertaken.

The IGY was carried out by the International Council of Scientific Unions while he was president in 1957-59.

In 1963, Berkner, with L.C. Marshall, advanced a theory to describe the way in which the atmospheres of the solar system's inner planets had evolved.

Beginning in 1926, as a naval officer, Berkner assisted in the development of radar and navigation systems, naval aircraft electronics engineering, and studies that led to the construction of the Distant Early Warning system, a chain of radar stations designed to give the United States advance warning in the event of a missile attack across the North Pole.

He wrote more than 100 papers and several books, including Rockets and Satellites (1958), Science in Space (1961), and The Scientific Age (1964).