Alfred Lee Loomis (November 4, 1887 – August 11, 1975) was an American attorney, investment banker, philanthropist, scientist, physicist, inventor of the LORAN Long Range Navigation System and a lifelong patron of scientific research. He established the Loomis Laboratory in Tuxedo Park, New York, and his role in the development of radar and the atomic bomb contributed to the Allied victory in World War II. He invented the Aberdeen Chronograph for measuring muzzle velocities, contributed significantly (perhaps critically, according to Luis Alvarez) to the development of a ground-controlled approach technology for aircraft, and participated in preliminary meetings of the Manhattan Project.
Loomis also made contributions to biological instrumentation. Working with E. Newton Harvey he co-invented the microscope centrifuge, and pioneered techniques for electroencephalography. In 1937, he discovered the sleep K-complex brainwave. During the Great Depression, Loomis anonymously paid the Physical Review journal's fees for authors who could not afford them.