William Hathaway (born February 21, 1924) is an American Democratic Party politician from Maine.
He was elected to the U.S. House as a Democrat and served in that body from 1965 until 1973. He then served as a member of the United States Senate from 1973 until 1979.
Hathaway was first elected to the House in 1964. He defeated incumbent U.S. Senator Margaret Chase Smith with a small majority in 1972, but was defeated for reelection in 1978 by Republican Congressman Bill Cohen.
Preceded by: Margaret Chase Smith U.S. Senator (Class 2) from Maine 1973-1979 Succeeded by: Bill Cohen Preceded by: Clifford G. McIntire Congressperson Maine's 2nd District 1965 - 1973 Succeeded by: Bill Cohen