Since 500 BC present-day Denmark is inhabited by Danish tribes. Danish Vikings establish power in the ninth century in England and Normandy and around 950 the Kingdom of Denmark becomes a fact. During the viking period (9th-11th centuries), Denmark is a great power based on the Jutland Peninsula, the Island of Zealand, and the southern part of what is now Sweden. In the early 11th century, king Canute unites Denmark and England for almost 30 years. From 1000 on Denmark occupies lots of areas, including Estonia and Norway, but it finally loses control over England. De facto Denmark is a feudal state. Since the Kalmar Union of 1397 the Kingdom of Denmark forms a personal union with Sweden and Norway. Sweden becomes independent in 1523. After the Napoleonic war Denmark has to secede Norway to Sweden in 1814.

Denmark remains an absolute monarchy until 1849 when it becomes a parliamentary monarchy. Though mostly liberals dominate parliament, the king appoints for long times conservatives as prime minister. Dominant prime ministers are Jakob Brønnum Scavenius Estrup (1875-1894), Kjeld Thor Tage Otto von Reedtz-Thott (1894-1897), Hugo Egmont Hørring (1897-1900) and Hannibal Sehested til Broholm (1900-1901). This changes in 1901 when Johan Hendrik Deuntzer of the liberal Venstrereformpartiet (Left Reform Party, VRP) becomes prime minister in a parliamentary government. VRP leads the government until 1909, with Jens Christian Christensen (1905-1908), Niels Thomasius Neergard (1908-1909) and Johan Ludvig Carl Christian, greve Holstein-Ledreborg (1909). After the defeat of his government in parliament in 1909, the leader of Radikale Venstre (Radical Left, RV), Carl Theodor Zahle, heads a minority government. He is succeeded in 1910 by Klaus Berntsen of the Venstre (Left) in 1910, but he regains the premiership in 1913. The radical government introduces universal suffrage in 1915. From 1918 on Denmark forms a personal union with its former colony of Iceland. In 1920 Neergard becomes prime minister again.

When Det Socialdemokratiscke Forbund (Social Democractic League, SDF) becomes the largest party in 1924, its leader Thorvald August Marinus Stauning become prime minister. For long times SDF will be the dominant party in Danish politics. This is interrupted by a coalition lead by Thomas Madsen-Mygdal of Venstre in 1926. Stauning becomes prime minister again in 1929 when the conservatives withdraw support of the Madsen-Mydgal government. From 1940 to 1945 Denmark is occupied by Germany. During this war Stauning is succeeded by his co-partisan Vilhelm Buhl in 1942 and by the non-partisan Erik Julius Christian Scavenius in 1942. Scavenius lays down his function in 1943, from then on Germany governs Denmark alone. During this occupation Iceland, occupied by the United States, leaves the personal union in 1944 and becomes independent.

After the war Vilhelm Buhl becomes prime minister again for some months. When SDF loses the 1945 elections he is succeeded by Knud Kristensen. The SDF, historically identified with well-organized labour movement but today appealing more broadly to the middle class, holds power either alone or in coalition from `147 tot 1968 under the premiership of Hans Hedtoft of the SDF (1947-1950 and 1953-1955), Hans Christian Hansen (1955-1960), Viggo Kampmann (1960-1962), and Jens Otto Krag (1962-1968 and 1971-1972). Under Kampmann the party is renamed Socialdemokratiet i Danmark (Social Democracy in Denmark, SD). This social-democratic rule is interrupted by a premiership of Erik Eriksen of Venstre (in a coalition with the Konservative Folkeparti (Conservative People's Party, KFP) between 1950 and 1953. A second interruption takes place when Radikale Venstre wins the 1968 Hilmar Baunsgaard can form a coalition of RV, Venstre and KFP.

In 1971 social-democratic rule starts again with Krag. He is succeeded by Anker Jørgensen in 1972. In 1973 SD loses the elections and Poul Hartling of Venstre can form a minority government. The same year Denmark joins the European Communities (renamed European Union. Anker Jørgensen regains the premiership in 1975 and holds this function until 1982. The elections of 1981 are won by the KFP. Poul Schlüter becomes prime minister in a coalition with Venstre and others until 1993. That year SD wins the elections and Poul Nyrup Rasmussen can form a government with RV and Socialistisk Folkpartiet (Socialist People's Party, SF). In 2001 Venstre wins the elections, which makes Anders Fogh Rasmussen prime minister in a coalition with the KF.