Joan Marjorie McLagan (née Langdon; December 2, 1922 – March 15, 2022) was a Canadian competitive swimmer and breaststroker. As McLagan reached the peak of her swimming career during World War II, she was forced to limit herself to competing at national and Pacific Northwest championships, as all major international meets were temporarily suspended during the war years. She was coached by fellow British Columbia Sports Hall of Fame member Percy Norman.