Mary Catherine Murphy (born October 25, 1939) is an American politician and member of the Minnesota House of Representatives. A member of the Minnesota Democratic–Farmer–Labor Party, she represents District 3B, which includes parts of Lake and St. Louis counties in the northeastern part of the state. She is a retired history and social studies teacher at Duluth Central High School in Duluth (1964–97). She is active in historical preservation and works as a grounds manager.