Malcolm Kenneth Macmillan (21 August 1913 – 17 November 1978) was a Scottish Labour Party politician and journalist.
At the 1935 general election, he was elected as Member of Parliament (MP) for the Western Isles. He was re-elected at the next seven general elections, serving as MP for 35 years before losing his seat at the 1970 general election to the Scottish National Party's Donald Stewart.
In 1972, Macmillan was expelled from the Labour Party after disagreement over the selection of his replacement as Labour candidate, Andrew Wilson. Macmillan stood as a United Labour Party candidate in the February 1974 general election, but came fourth, polling only 6.8% of the vote while the SNP substantially increased their majority.