King Frederick VI of Denmark and Norway (January 28, 1768 – December 3, 1839), reigned as King of Denmark from 1808 to 1839, and as king of Norway from 1808 to 1814. He also served as Regent of Denmark from 1784 to 1808 under his father's name. His father, Christian VII, had major psychological problems, including suspected schizophrenia, that resulted in his standing down from power for most of his reign.

During the regency, Frederick instituted widespread liberal reforms with the assistance of Chief Minister Andreas Peter Bernstorff, including the abolition of serfdom. Crises encountered during his reign include disagreement with the British over neutral shipping. This resulted in two British attacks on Danish shipping in 1801 and 1807. The former attack is known as the Battle of Copenhagen.

His wife was Marie Sophie Friederike of Hesse-Cassel, a member of a German family with close marriage links with the Royal families of both Denmark and Great Britain. They married in 1790 and had eight children. One of them, Princess Wilhelmine, became the wife of Frederick VII of Denmark. However, none of Frederick VI's sons survived infancy and when he died, he was succeeded by his cousin, Christian VIII of Denmark.

He was known as a patron of astronomy and in 1832 offered gold medal prizes to anyone who discovered a comet using a telescope. His successors continued this until 1850. The prize was terminated in the aftermath of the First War of Schleswig.