Christian was born at Christiansborg Palace in Copenhagen. He was the eldest son of Hereditary Prince Frederick of Denmark and Norway and Duchess Sophia Frederica of Mecklenburg-Schwerin. His paternal grandparents were King Frederick V of Denmark-Norway and his second wife, Duchess Juliana Maria of Brunswick-Wolfenbüttel.
Christian's mother died in 1794 when he was eight years old, and his father died in 1805 when Christian was nineteen. His upbringing was marked by a thorough and broad-spectrum education with exposure to artists and scientists who were linked to his father's court. Christian inherited the talents of his highly gifted mother, and his amiability and handsome features are said to have made him very popular in Copenhagen.
Christian first married his cousin Duchess Charlotte Frederica of Mecklenburg-Schwerin at Ludwigslust on 21 June 1806. Charlotte Frederica was a daughter of Friedrich Franz I, Grand Duke of Mecklenburg-Schwerin, and Princess Louise of Saxe-Gotha-Altenburg. His first-born son was Christian Frederik, who was born and died at Schloss Plön on 8 April 1807. His second son became Frederick VII of Denmark. The marriage was dissolved by divorce in 1810 after Charlotte Frederica was accused of adultery.
Christian married his second wife, Princess Caroline Amalie of Schleswig-Holstein-Sonderburg-Augustenburg (daughter of Louise Augusta of Denmark, the only sister of Frederick VI) at Augustenborg Palace on 22 May 1815. The couple was childless and lived in comparative retirement as leaders of the literary and scientific society of Copenhagen until Christian ascended the throne of Denmark. 
Christian had ten extramarital children, for whom he carefully provided. It is rumored that these extramarital children included the fairy tale author Hans Christian Andersen, though there is little evidence to support this.
In May 1813, as the heir presumptive of the kingdoms of Denmark and Norway, Christian was sent as stattholder (the king's highest representative in Norway) to Norway to promote the loyalty of the Norwegians to the House of Oldenburg, which had been very badly shaken by the disastrous results of Frederick VI's adhesion to the falling fortunes of Napoleon I of France. Christian did all he could personally to strengthen the bonds between the Norwegians and the royal house of Denmark. Though his endeavours were opposed by the so-called Swedish party, which desired a dynastic union with Sweden, he placed himself at the head of the Norwegian party of independence after the Treaty of Kiel had forced the king to cede Norway to the king of Sweden. He was elected Regent of Norway by an assembly of notables on 16 February 1814.
This election was confirmed by the Norwegian Constituent Assembly convoked at Eidsvoll on 10 April, and on 17 May the constitution was signed and Christian was unanimously elected king of Norway under the name Christian Frederick (Kristian Frederik in Norwegian). Christian next attempted to interest the great powers in Norway's cause, but without success. On being pressed by the commissioners of the allied powers to bring about a union between Norway and Sweden in accordance with the terms of the treaty of Kiel, and then return to Denmark, he replied that, as a constitutional king, he could do nothing without the consent of the parliament (Storting), which would not be convoked until there was a suspension of hostilities on the part of Sweden.
Sweden refused Christian's conditions and a short military campaign ensued in which the Norwegian army was defeated by the forces of the Swedish crown prince Charles John. The brief war concluded with the Convention of Moss on 14 August 1814. By the terms of this treaty, King Christian Frederick transferred executive power to the Storting, then abdicated and returned to Denmark. The Storting in its turn adopted the constitutional amendments necessary to allow for a personal union with Sweden and on 4 November elected Charles XIII of Sweden as the new king of Norway.
On 3 December 1839 he ascended the Danish throne as Christian VIII. The Liberal party had high hopes of “the giver of constitutions,” but he disappointed his admirers by steadily rejecting every Liberal project. Administrative reform was the only reform he would promise. In his attitude to the growing national unrest in the twin duchies of Schleswig and Holstein he often seemed hesitated and half-hearted, which damaged his position there. It was not until 1846 that he clearly supported the idea of Schleswig being a Danish area.
King Christian VIII continued his predecessor's patronage of astronomy, awarding gold medals for the discovery of comets by telescope and financially supporting Heinrich Christian Schumacher with his publication of the scientific journal Astronomische Nachrichten. It was during his reign that the last remnants of Danish India, namely Tranquebar in the south and Serampore in Bengal, were sold to the British in 1845.
His only legitimate son, the future Frederick VII (1808–1863) was married three times, but produced no legitimate issue. Since he was apparently unlikely to beget heirs, Christian wished to avert a succession crisis. Christian commenced arrangements to secure the succession in Denmark. The result was the selection of the future Christian IX as hereditary prince, the choice made official by a new law enacted on 31 July 1853 after an international treaty made in London.
King Christian died of blood poisoning in Amalienborg Palace in 1848 and was interred in Roskilde Cathedral. Some historians and biographers believe that King Christian would have given Denmark a free constitution had he lived long enough; his last words are sometimes (rather tragically) recorded as "I didn't make it". (Jeg nåede det ikke) 
|Ancestors of Christian VIII of Denmark|
Christian VIII of DenmarkBorn: 18 September 1786 Died: 20 January 1848
| King of Denmark
Duke of Schleswig, Holstein
3 December 1839 – 20 January 1848
| King of Norway
17 May – 10 October 1814
Frederik of Hesse
| Governor-General of Norway
1 May 1813 – 16 February 1814
Hans Henric von Essen