Margaret I (Danish: Margrete Valdemarsdatter, Norwegian: Margrete Valdemarsdatter, Swedish: Margareta Valdemarsdotter, Icelandic: Margrét Valdimarsdóttir), (March 1353 – 28 October 1412), was Queen of Denmark, Norway and Sweden and founder of the Kalmar Union, which united the Scandinavian countries for over a century. She acted as queen regnant of Denmark, although in those days it was not the Danish custom for a woman to reign.