Christian IV (Danish: Christian den Fjerde; 12 April 1577 – 28 February 1648), was king of Denmark-Norway and Duke of Holstein and Schleswig from 1588 to 1648. His 59-year reign is the longest of Danish monarchs, and of Scandinavian monarchies. A member of the house of Oldenburg, Christian began his personal rule of Denmark in 1596 at the age of 19. He is frequently remembered as one of the most popular, ambitious, and proactive Danish kings, having initiated many reforms and projects. Christian IV obtained for his kingdom a level of stability and wealth that was virtually unmatched elsewhere in Europe. He engaged Denmark in numerous wars, most notably the Thirty Years' War (1618–48), which devastated much of Germany, undermined the Danish economy, and cost Denmark some of its conquered territories. Christian was born at Frederiksborg Castle in Denmark on 12 April 1577 as the third child and eldest son of King Frederick II of Denmark–Norway and Sofie of Mecklenburg-Schwerin. He was descended, through his mother's side, from king John of Denmark, and was thus the first descendant of King John to assume the crown since the deposition of King Christian II. At the time, Denmark was still an elective monarchy, so in spite of being the eldest son Christian was not automatically heir to the throne. However, in 1580, at the age of 3, his father had him elected Prince-Elect and successor to the throne. At the death of his father on 4 April 1588, Christian was 11 years old. He succeeded to the throne, but as he was still under-age a regency council was set up to serve as the trustees of the royal power while Christian was still growing up. It was led by chancellor Niels Kaas. At the death of Niels Kaas in 1594, Jørgen Rosenkrantz took over leadership of the regency council. In 1595, the Council of the Realm decided that Christian would soon be old enough to assume personal control of the reins of government. On 29 August 1596, Christian IV was crowned at the Church of Our Lady in Copenhagen by the Bishop of Zealand, Peder Jensen Vinstrup. On 30 November 1597, he married Anne Catherine of Brandenburg, a daughter of Joachim Friedrich, Margrave of Brandenburg and Duke of Prussia.

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