Elmer Belt (April 10, 1893 – May 17, 1980) was an internationally recognized urologist, a pioneer in sex-change surgery, an important mover in the founding of the UCLA School of Medicine, and a book collector known for assembling a library of research materials about Leonardo da Vinci—the Elmer Belt Library of Vinciana—which he donated to the University of California, Los Angeles between 1961-66.