Dagmar Rehak (born 16 January 1956) is a retired German breaststroke swimmer who won a bronze medal at the 1977 European Aquatics Championships. She competed at the 1976 Summer Olympics in the 100 m and 200 m breaststroke and 4 × 100 m medley relay events but did not reach the finals. During her career she won six national titles in the 100 m (1974, 1977, 1980) and 200 m (1974, 1975, 1978) breaststroke. She missed the 1980 Summer Olympics because of their boycott by West Germany.