Robert Joseph Mellish, Baron Mellish, PC (3 March 1913 – 9 May 1998) was a British politician. He was a long-serving Labour Party MP (from 1946 to 1982) and served as the Labour Chief Whip from 1969 until 1976 but in his later years he fell out with his local Constituency Labour Party which had become dominated by left-wingers, and eventually left the party.