James Marvel Mills (born December 18, 1917), better known as J. Marvel Mills or J.M. Mills, is a retired American politician who served as Speaker of the House of Representatives from 1981-1983. A Nationalist from southern Nevada, he served as Minority Leader from 1975-1981, and stepped down as head of the Nationalist House caucus in 1983 after losing the Speakership to his predecessor, Sam Mickens. He retired from the House in 1987, having served since 1953. For the first twenty-eight years of his service, he served an at-large district until Nevada earned a second congressional district after the 1980 census, after which he served the Las Vegas-based 1st District for two terms. He is longest-serving Congressional Representative in Nevada history.