William F. Downes (born 1946) is a retired United States federal judge.Born in Boston, Massachusetts, Downes received a B.A. from the University of North Texas in 1968 and served in the U.S. Marine Corps from 1968 to 1971. He received a J.D. from the University of Houston Law Center in 1974. He was in private practice in Green River, Wyoming from 1975 to 1978 and in Casper, Wyoming from 1978 to 1994.