Thomas Michael McMillan, PC (born October 15, 1945) is a Canadian political scientist and former politician, the country's third-longest-serving Minister of the Environment (after John Roberts under Pierre Trudeau and Catherine McKenna under Justin Trudeau), in office from 1985 to 1988. A member of the Progressive Conservative Party of Canada, he was the Member of Parliament (MP) for Hillsborough from 1979 until 1988. McMillan is a graduate of St. Dunstan's University (now part of UPEI) and Queen's University (master's in political studies) and has a doctorate in humane letters, honoris causa, from Bridgewater State University.