James Alfred Van Allen (September 7, 1914 – August 9, 2006) was an American space physicist at the University of Iowa. He was instrumental in establishing the field of magnetospheric research in space.

The Van Allen radiation belts were named after him, following his discovery using Geiger–Müller tube instruments on the 1958 satellites (Explorer 1, Explorer 3, and Pioneer 3) during the International Geophysical Year. Van Allen led the scientific community in putting scientific research instruments on space satellites.

James Van Allen was born on September 7, 1914, on a small farm near Mount Pleasant, Iowa. As a child, he was fascinated by mechanical and electrical devices and was an avid reader of Popular Mechanics and Popular Science magazines. He once horrified his mother by constructing a Tesla coil that produced foot-long sparks and caused his hair to stand on end.

A fellowship allowed him to continue studying nuclear physics at the Carnegie Institution in Washington, D.C., where he also became immersed in research in geomagnetism, cosmic rays, auroral physics and the physics of Earth's upper atmosphere.

In August 1939, Van Allen joined the Department of Terrestrial Magnetism (DTM) of the Carnegie Institution in Washington, D.C. as a Carnegie Research Fellow. In the summer of 1940, he joined DTM's national defense efforts with his appointment to a staff position in Section T with the National Defense Research Committee (NDRC) in Washington, D.C., where he worked on the development of photoelectric and radio proximity fuzes, which are detonators that increase the effectiveness of anti-aircraft fire. Another NDRC project later became the atomic bomb Manhattan Project in 1941. With the outbreak of World War II, the proximity fuze work was transferred to the newly created Applied Physics Laboratory (APL) of Johns Hopkins University in April 1942. He worked on improving the ruggedness of vacuum tubes subject to the vibration from a gun battery. The work at APL resulted in a new generation of radio-proximity fuses for anti-aircraft defense of ships and for shore bombardment.

Van Allen was commissioned as a U.S. Navy lieutenant in November 1942 and served for 16 months on a succession of South Pacific Fleet destroyers, instructing gunnery officers and conducting tests on his artillery fuses. He was an assistant staff gunnery officer on the battleship USS Washington when the ship successfully defended itself against a Japanese attack during the Battle of the Philippine Sea, (June 19–20, 1944). For his actions at the Pacific, Van Allen was awarded four battle stars. He was promoted to lieutenant commander in 1946. "My service as a naval officer was, far and away, the most broadening experience of my lifetime," he wrote in a 1990 autobiographical essay.

Discharged from the Navy in 1946, Van Allen returned to civilian research at APL. He organized and directed a team at Johns Hopkins University to conduct high-altitude experiments, using V-2 rockets captured from the Germans at the end of World War II. Van Allen decided a small sounding rocket was needed for upper atmosphere research. The Aerojet WAC Corporal and the Bumblebee missile were developed under a US Navy program. He drew specifications for the Aerobee sounding rocket and headed the committee that convinced the U.S. government to produce it. The first instrument-carrying Aerobee was the A-5, launched on March 5, 1948, from White Sands, New Mexico, carrying instruments for cosmic radiation research, reaching an altitude of 117.5 km.

Van Allen was elected chairman of the V-2 Upper Atmosphere Panel on December 29, 1947. The panel was renamed Upper Atmosphere Rocket Research Panel on March 18, 1948; then Rocket and Satellite Research Panel on April 29, 1948. The panel suspended operations on May 19, 1960, and had a reunion on February 2, 1968.