List of all of the Norwegian Queens:
http://www.vg.no/pub/vgart.hbs?artid=209690
Here's a little history about the last Queen regent:
In 1368-70 Valdemar Atterdag had gained courage enough to challenge the Hanseatic League. Denmark tried to master the southwestern Baltic and end the Hansa's economic control there. But instead the League was united (the Cologne-federation) and decided to raise an armed force that then defeated the Danes decisively. The league then tried to dominate Denmark by means of a 15 year's contracted possession of castles and towns along Öresund.
After Valdemar Atterdag's death his five years old grandson Olav is elected King of Denmark - the alternative would have been the nephew of King Albrecht supported by the German emperor. But the emperor died. Olav's father was King Håkon of Norway, but the Danish realm is in the hands of his mother, Queen Margrete of Norway, the daughter of Valdemar Atterdag, who wasn't on speaking terms with her husband the king.
When King Håkon died his son Olav was still under age, only nine years old, and the queen ruled over both Norway and Denmark. The King Olav died however also (at the age of seventeen) and the son-son of the Swedish King Albrecht of Mecklenburg was closest to the throne.
The Danish nobility did however prefer the Norwegian queen for the German king and appointed her to regent with support of the Thing in Lund. Then the Norwegians elected her to regent, and finally the Swedish State Council and aristocracy chose to support her against King Albrecht in Sweden, who was beaten in a battle with Queen Margrete and together with his son Erik captured and imprisoned. (1395 he was rescued through Mecklenburg's war against the queen.)
Finally Bugislav, the nephew of Queen Margrete, is elected king (known as Erik of Pomerania) by the Norwegian state council with the queen as regent until he comes to age; then he is elected king in province after province of Denmark (1387) and so also by the Swedish state council (1389). Thereby the union was made legitimate, and in contrast to earlier occasions when one king ruled over two Scandinavian countries, this came to last for a long time.