Julius Edgar Lilienfeld (April 18, 1882 – August 28, 1963) was an American electrical engineer and physicist who has been credited with the first patent on the field-effect transistor in 1925.

Additionally, because of his failure to publish articles in learned journals and since high-purity semiconductor materials were not available to him, his FET patent never achieved fame, causing confusion for later inventors.

[1] In the United States Lilienfeld did research on anodic aluminum oxide films, patenting the electrolytic capacitor in 1931, the method continuing to be used throughout the century.

After it closed in 1935, he and his wife built a house on St. Thomas in the U.S. Virgin Islands in hope of escaping an allergy associated with wheat fields, from which Lilienfeld had suffered for most of his life.

Lilienfeld frequently traveled between St. Thomas and various mainland locations and continued to test new ideas and patent the resulting products.