Margaret I (Danish: Margrete Valdemarsdatter, Bokmål: Margrete Valdemarsdatter, Nynorsk: Margrete Valdemarsdotter, Swedish: Margareta Valdemarsdotter, Icelandic: Margrét Valdimarsdóttir; 15 March 1353 – 28 October 1412) was queen consort of Norway (1363–1380) and Sweden (1363–1364) and later ruler in her own right of Denmark, Norway and Sweden, from which later period there are ambiguities regarding her specific titles.
She was the founder of the Kalmar Union, which spanned Scandinavia for over a century.
Margaret was known as a wise, energetic and capable leader, who governed with "farsighted tact and caution," earning the nickname "Semiramis of the North".
She was derisively called "King Breechless", one of several mean nicknames invented by her rival Albert of Mecklenburg, but was also known by her subjects as "the Lady King", which became widely used in recognition of her capabilities.
Knut Gjerset calls her "the first great ruling queen in European history."The youngest daughter of King Valdemar IV of Denmark, Margaret was born at the Søborg Castle.
She was a practical, patient administrator and diplomat, albeit one of high aspirations and a strong will, who intended to unite Scandinavia forever into one single entity with the strength to resist and compete against the might of the Hanseatic League.
She died childless, having survived her only son, Olaf II,.
Margaret was ultimately succeeded by a string of more or less competent monarchs, after her efforts to raise and educate her heir Eric of Pomerania and his bride Philippa of England.
Philippa in particular was an excellent pupil.
"Although Eric came of age in 1401, Margaret continued for the remaining 11 years of her life to be sole ruler in all but name.
[Her] second regency marked the beginning of a Dano-Norwegian Union which was to last for more than four centuries." Ultimately, the Union into which she put so much effort and hope gradually disintegrated.
Some Norwegian and Swedish historians have criticized Margaret for favouring Denmark and being too autocratic, though she is generally thought to have been highly regarded in Norway and respected in Denmark and Sweden.
She was painted in a negative light in contemporary religious chronicles, as she had no qualms suppressing the Church to promote royal power.
Margaret is known in Denmark as "Margrethe I" to distinguish her from the current queen, who chose to be known as Margrethe II in recognition of her predecessor.