Donald Sage Mackay, Baron Mackay of Drumadoon, PC, QC (30 January 1946 – 21 August 2018) was a British judge of the Supreme Courts of Scotland, and a Lord Advocate, the country's senior Law Officer. He was also one of five additional Lords of Appeal in the House of Lords, where he sat as a crossbencher. He was the brother of the BBC news reporter Alan Mackay.