John R. Tucker (1946 – April 12, 2014) was an American physicist who made several contributions to the fields of electronics, physics and microwave theory, known for generalizing the microwave mixer theory and presenting the body of work, known as the "Tucker theory", and for his fundamental theoretical contributions which resulted into various advancements in experimental Submillimeter astronomy. He is also credited with laying down some of the technological foundations (a number of novel semiconductor devices and fabrication techniques) for making practical Quantum computing possible.