Hyman G. Rickover was an admiral in the U.S. Navy. He directed the original development of naval nuclear propulsion and controlled its operations for three decades as director of the U.S. Naval Reactors office. In addition, he oversaw the development of the Shippingport Atomic Power Station, the world's first commercial pressurized water reactor used for generating electricity. Rickover is also one of four people who have been awarded two Congressional Gold Medals.
Rickover is known as the "Father of the Nuclear Navy," and his influence on the Navy and its warships was of such scope that he "may well go down in history as one of the Navy's most important officers." He served in a flag rank for nearly 30 years, ending his career as a four-star admiral. His years of service exceeded that of each of the U.S. Navy's five-star fleet admirals—Leahy, King, Nimitz and Halsey—all of whom served on active duty for life after their appointments. Rickover's total of 63 years of active duty service make him the longest-serving naval officer, as well as the longest-serving member of the U.S armed forces in history.