Margaret I (March 1353 – 28 October 1412), is Queen of Denmark, Norway and Sweden and founder of the Kalmar Union, which unites he Scandinavian countries for over a century.

She acts as queen regnant of Denmark, although at this time it is not the Danish custom for a woman to reign.

Her title in Denmark is derived from her father King Valdemar IV of Denmark.

She becomes Queen of Norway and Sweden by virtue of her marriage to King Haakon VI of Norway.