Marcel Cadieux (June 17, 1915 - March 19, 1981) was a Canadian civil servant and diplomat.
He joined the Department of External Affairs in 1941. From 1964 to 1970 he was Under-Secretary of State for External Affairs. He was was Canada's first francophone Ambassador to the United States from 1970 to 1975.
In 1969 he was made a Companion of the Order of Canada.
He married Anita Comtois and they had two sons.
