Lee Warren Metcalf (January 28, 1911 – January 12, 1978) was an American lawyer, judge, and politician. A member of the Democratic Party, he served as a U.S. Representative (1953–1961) and a U.S. Senator (1961–1978) from Montana. He was Permanent Acting President pro tempore of the Senate, the only person to hold that position, from 1963 until his death in 1978.