Theresa Michalak (born 7 May 1992) is a German competitive swimmer and former European champion. She represented Germany at the 2012 Summer Olympics in London, competing in the 200-metre individual medley and 4×200-metre freestyle relay. Michalak holds the German records for the 100-metre and 200-metre individual medley. She won the gold medal in the 100-metre individual medley at the 2011 European Short Course Swimming Championships.