William B. O'Gara (born December 6, 1931) is an American schoolteacher and politician from Maine. O'Gara, a Democrat, served in the Maine State Senate from 1996 to 2002, representing his residence in Westbrook, Maine and nearby areas of Cumberland County. He was defeated for re-election in 2002 by Republican Carolyn Gilman. From 1974 to 1984, O'Gara served as Mayor of Westbrook.