| Birth Date: | 20 November 1924 |
| Birth Place: | Skovshoved, Denmark |
| Death Date: | [1] |
| Death Place: | Copenhagen, Denmark |
| Sport: | Swimming |
| Club: | DKG, København |
| Show-Medals: | yes |
Karen Margrethe Harup Petersen (20 November 1924 – 9 July 2009)[2] was a Danish swimmer. She competed in four events at the 1948 Summer Olympics and won three medals: a gold in the 100 m backstroke and silvers in the 400 m and 4 × 100 m freestyle, placing fourth in the 100 m freestyle.
She won three more gold medals at the 1947 European Championships.[3] During her career she held 30 national titles and set two world records in freestyle relay events. In 1949, she retired from competitions and started a five decades long career of a swimming coach. In 1975, she was inducted into the International Swimming Hall of Fame.[4] [5]