Robert Alexander MacKay (January 2, 1894 – November 25, 1979) was a Canadian political scientist and diplomat.
During the Second World War, MacKay worked for the Department of External Affairs.
After the Second World War, MacKay rejoined the Department of External Affairs in 1947.
He was Canada's Permanent Representative to the United Nations from 1955 to 1958 and Canadian Ambassador to Norway from 1958 to 1961.
He was the father of William Andrew MacKay.