The son of the mentally incompetent king Christian VII and Queen Caroline Matilda, Frederick was reared largely by his father's stepmother, the queen dowager Juliana Maria, who, with her son Prince Frederick and Ove Höegh-Guldberg, virtually ruled Denmark until 1784. In April of that year the Crown Prince brought about changes in the government that transferred the real power to him. Frederick supported reform measures to grant personal liberty and legal protection to the peasants and instituted several other social and economic reforms. Married in 1790 to Maria Sophia Frederica, daughter of the landgrave Charles of Hesse, Frederick acceded to the throne upon his father's death on March 13, 1808.

After his accession he inclined more to personal rule, and the cabinet's influence decreased. Initially neutral in the Napoleonic Wars, Frederick supported Napoleon after the English bombardment of Copenhagen in 1807. An indifferent diplomat, he supported Napoleon too long and failed to take advantage of Sweden's difficulties in 1809. At the Peace of Kiel (January 1814), he had to cede Norway to Sweden and Heligoland to England. In the lean years following the Congress of Vienna, Frederick proved himself an energetic, responsible, and upright “father of his country.” Under the influence of the July Revolution of 1830 in France, Frederick, in 1834, set up four consultative provincial assemblies. This action marked the beginning of parliamentary life in Denmark.