Michael Clarence McMahon, Sr. (February 1, 1915 – December 3, 1974) was a Canadian professional ice hockey defenceman who played 57 games in the National Hockey League. Born in Brockville, Ontario, he played for the Montreal Canadiens and Boston Bruins. He won the Stanley cup in 1944 with the Montreal Canadiens.
He played senior hockey from 1935 to 1943 for the Brockville Magedomas, Cornwall Flyers, Quebec Aces, Montreal Royals, and the Ottawa Commandos. In 1942-43 he turned pro in the playoffs with the Montreal Canadiens.
McMahon played all of the 1943-44 season with Montreal and won the Stanley Cup. In 1944-45 he was back down with the Montreal Royals but he played 13 games with the Canadiens in 1945-46. He also played 2 games for the Boston Bruins as part of a previous trade.
After 1946 he played three seasons in the minor pros. He was the player-coach of the Houston Huskies in 1947-48. He retired in 1949.
In 57 NHL games he scored 7 goals and 18 assists.
His son Mike McMahon, Jr. also played in the NHL.