Margaret of Denmark (1353-1412) was a significant historical figure in Northern Europe, known for her role as a queen and a political leader. She was the daughter of King Valdemar IV of Denmark and became the queen consort of Haakon VI of Norway. Her marriage helped strengthen the ties between Denmark and Norway. Margaret later became the de facto ruler of both kingdoms after the death of her husband. She is best known for uniting the three kingdoms of Denmark, Norway, and Sweden under the Kalmar Union in 1397, which aimed to create a strong Scandinavian alliance.