The United Monarchy was a personal union between the Kingdom of Denmark and the duchy of Schleswig-Holstein and Lauenburg from 1850-1864.

When Denmark lost Norway in 1814 it was thereafter made up of the three duchies Schleswig, Holstein and Lauenburg, as well as a few tropical Colonies, Greenland, the Faroe Islands and Iceland. Throughout the 1800s, the issue of how these different parts of the country were to interconnect was discussed.

The political arguments of the United Monarchy were based on the king as a uniting figure. However, the king of Denmark was not king of the duchies - only the duke - and therefore, the United Monarchy became more of a personal union. The union still united the country since it was ruled by the same ruler, the king of Denmark. 

The united monarchy had the support of the conservative official circle as well as among some aristocrats in Denmark and the duchy. 

The United Monarchy-policy was a controversial and much discussed subject in the 1850s and the beginning of the 1860s. The idea of a United Monarchy-policy failed when Denmark lost the second war in Schleswig in 1864. In this war, the danes lost to Prussia and Austria and was forced to surrender their territories in the Southern parts of Jutland - including the duchies. Hereafter, the thought of a United Monarchy was abandoned.

By some, the United Monarchy is perceived as being a period in Danish history between 1773 and 1814, where the king of Denmark and Norway achieved unlimited control over the duchies. Here, the idea of an United Monarchy could be seen as an attempt to united the Scandinavian people: the Danes, Norwegians, Germans, Jews, the Sami people and other minorities, who was subjects to the rule of the king of Denmark and Norway in this period.