John Mahaffy (born July 18, 1919) is a retired professional ice hockey centre who played 37 games in the National Hockey League. Born in Montreal, Quebec, he played for the New York Rangers and Montreal Canadiens.
He played for the Montreal Junior Royals from 1934 to 1936 and then graduated to the senior Montreal Royals. Escept for the 1938-39 season with the Streatham Redskins in Great Britain, Mahaffy played for the Royals through the 1944-45 season.
In 1942-43 he was called up to the Montreal Canadiens where he scored 2 goals and 5 assists in 9 games. In 1943 he was loaned to the New York Rangers as part of the deal that brought Phil Watson to the Habs. He scored 9 goals and 20 assists in 28 games for the Rangers.
Except for one playoff game for the Canadiens in 1944-45, Mahaffy spent the rest of his career in the senior and minor pro ranks. He retired in 1953.