Harald Bluetooth in the context of "House of Knýtlinga"

The Evangelical-Lutheran Church in Denmark or National Church (Danish: Folkekirken lit. 'the People's Church', or unofficially den danske folkekirke, 'the Danish People's Church'; Greenlandic: Ilagiit lit. 'the Congregation'), sometimes called the Church of Denmark, is the established, state-supported church in Denmark. The supreme secular authority of the church is composed of the reigning monarch and Denmark's Parliament, the Folketing. As of 2025, 70.7% of the population of Denmark are members, though membership is voluntary.

Christianity was introduced to Denmark in the 9th century by Ansgar, Archbishop of Hamburg-Bremen. In the 10th century, King Harald Bluetooth became Christian and began organizing the church, and by the 11th century, the country was fully Christianized. Since the Reformation in Denmark, the church has been Lutheran, while retaining much of its high church pre-Reformation liturgical traditions.

Swein Forkbeard (also Sweyn, died 3 February 1014) was King of Denmark from 986, King of England for five weeks from December 1013, and King of Norway from 999/1000, all until his death in 1014. He was the father of King Harald II of Denmark, King Cnut the Great, and Queen Estrid Svendsdatter.

In the mid-980s, Swein revolted against his father, Harald Bluetooth, and seized the throne. Harald was driven into exile and died shortly afterwards in November 986 or 987. In 1000, with the allegiance of Eric, Earl of Lade, Swein ruled most of Norway. In 1013, shortly before his death, he became the first Danish king of the English after a long effort.

The history of Denmark as a unified kingdom began in the 8th century, but historic documents describe the geographic area and the people living there—the Danes—as early as 500 AD. These early documents include the writings of Jordanes and Procopius. With the Christianization of the Danes c. 960 AD, it is clear that there existed a kingship. King Frederik X can trace his lineage back to the Viking kings Gorm the Old and Harald Bluetooth from this time, thus making the Monarchy of Denmark the oldest in Europe. The area now known as Denmark has a rich prehistory, having been populated by several prehistoric cultures and people for about 12,000 years, since the end of the last ice age.

Denmark's history has particularly been influenced by its geographical location between the North and Baltic seas, a strategically and economically important placement between Sweden and Germany, at the center of mutual struggles for control of the Baltic Sea (dominium maris baltici). Denmark was long in disputes with Sweden over control of Skånelandene and with Germany over control of Schleswig (a Danish fief) and Holstein (a German fief).

The Christianization of Scandinavia, as well as other Nordic countries and the Baltic countries, took place between the 9th and the 12th centuries. The realms of Denmark, Norway and Sweden established their own archdioceses, responsible directly to the pope, in 1104, 1154 and 1164, respectively. The conversion to Christianity of the Scandinavian people required more time, since it took additional efforts to establish a network of churches.

The earliest signs of Christianization were in the 830s with Ansgar's construction of churches in Birka and Hedeby. The conversion of Scandinavian kings occurred over the period 960–1020. Subsequently, Scandinavian kings sought to establish churches, dioceses and Christian kingship, as well as destroy pagan temples. Denmark was the first Scandinavian country to Christianize, as Harald Bluetooth declared this around AD 965, and raised the larger of the two Jelling Stones. According to historian Anders Winroth, Christianity was not forced upon Scandinavians by foreign states or foreign missionaries, but instead willfully adopted by Scandinavian kings who saw the religion as politically advantageous.

The monarchy of Denmark is a constitutional institution and an office of the Kingdom of Denmark. The Kingdom includes Denmark proper and the autonomous territories of the Faroe Islands and Greenland. The Kingdom of Denmark was already consolidated in the 8th century, whose rulers are consistently referred to in Frankish sources (and in some late Frisian sources) as "kings" (reges). Under the rule of King Gudfred in 804 the Kingdom may have included all the major provinces of medieval Denmark.

The current unified Kingdom of Denmark was founded or re-united by the Viking kings Gorm the Old and Harald Bluetooth in the 10th century. Originally an elective monarchy, it became hereditary only in the 17th century during the reign of Frederick III. A decisive transition to a constitutional monarchy occurred in 1849 with the writing of the first democratic constitution, replacing the vast majority of the old absolutist constitution. The current Royal House is a branch of the ducal House of Glücksburg, originally from Schleswig-Holstein in modern-day Germany, the House of Glücksburg itself being a collateral branch of the House of Oldenburg. The House of Glücksburg also produced the monarchs of Norway, of the United Kingdom and the former monarch of Greece in the direct male line.

The legendary kings of Denmark were, according to legend, the monarchs of Denmark, the Danes, or specific lands of Denmark (Zealand, Jutland or Scania) who preceded Gorm the Old, a king who reigned c. 930s to c. 960s and is the earliest reliably attested Danish ruler. Gorm's son, Harald Bluetooth, oversaw the widespread Christianization of Denmark, meaning that the legendary kings listed here are those from before Christianization and are predominantly (but not entirely) pagan. Kings preceding Gorm may be partly historical (especially those near to Gorm's time), but are either semi-legendary or entirely mythological. Some are based on earlier euhemerised stories (that is, figures from mythological folktales were depicted as historical kings by medieval writers such as Saxo Grammaticus).

There are many medieval accounts of the Danish kings of the Dark Ages, and these accounts can be confusing and contradictory (although there is overlap and different sources can include the same kings). This article presents the legendary kings from each source separately.