William Le Roy Emmet (July 10, 1858 -September 26, 1941) was an electrical engineer who made major contributions to alternating current power systems including the design of large rotary converters.
He graduated from the United States Naval Academy in 1881. He joined the Edison General Electric Company in 1891. Three years later, after a merger, he became employee of General Electric Company (GE). Emmet was a leading advocate of the electrical propulsion of ships from turbines. His systems were first used in American ships during World War I. He also developed the mercury vapour turbine system for electric power production.