At the age of eleven in 1588, having been elected successor in 1584, he became king. During his minority, his mother, Queen Sophie, became Regent and, assisted by four councillors, ruled the country while he was brought up by his maternal grandparents in Mecklenburg, where he received a good education. 
Queen Sophie supervised her son's education from a distance. She also arranged the marriages of her four daughters, one of whom, Anna, became Queen of England, and invested her own dowry so well she could leave her son a large fortune when she died in 1631. In 1596 he was declared to be of age. Dutiful, learned, athletic, interested in art and music, he also loved alcohol and "other" frivolous pursuits. He called Dutch engineers to build fortresses throughout Denmark as well as making considerable improvements to Copenhagen itself. 
In 1612 he lost his wife, Anna Catharina von Brandenburg, and in 1615 married his mistress, Christine Munk, who became Countess of Schleswig and Holstein. Christine already had borne him children, 
which she continued to do after their marriage. She had great influence until 1628 when it became known that she had had a fling with a German army officer and in 1630 was divorced. Yet at the same 
time Christian IV had produced children by Vibeke Kruse who was one of Christine's maids. 

Denmark became involved in the Thirty Years' War. The results were favourable for Denmark as Holstein, which had previously been lost, was restored. In 1643, however, war with Sweden again lost Denmark some Territories. 
In February 1648 he fell ill while at Frederiksborg and was taken by litter to Rosenborg Castle in Copenhagen. Here he died, 28 February 1648, attended by his favourite daughter, Leonore Christine, borne by Christine Munk in 1621 after their morganatic marriage. 
 

Source: Leo van de Pas