• Born date: 1860-03-07
• Born in: Sydenham, Ontario
• Death date: 1920-04-25
• Death in: Edmonton (provincial electoral district)

Alexander Grant MacKay (March 7, 1860 – April 25, 1920) was a Canadian teacher, lawyer and provincial level politician. He served prominent posts in two provincial legislatures as Leader of the Opposition in Ontario and as a Cabinet Minister in Alberta.