Karin Kessler (née Rettmeyer; born 25 March 1939) is a German female former track and field athlete who competed for West Germany in the 800 metres. She was the gold medallist in that event at the 1967 European Indoor Games, having been runner-up to Zsuzsa Szabó the previous year at the 1966 European Indoor Games. Kessler also represented her country at the 1966 European Athletics Championships, reaching the semi-finals. She set a personal best of 2:03.6 minutes in 1967, which was a West German record for the Hamburg-born athlete.