Thyra was the wife of King Gorm the Old of Denmark, and one of the first queens of Denmark widely believed by scholars to be historical rather than legendary. She is presented in medieval sources as a wise and powerful woman who ordered the building or fortification of the Danevirke, consistent with her commemoration on multiple Viking Age runestones. These include those at Jelling which was the seat of power for her dynasty. When she was born and became queen is unclear, however, she likely ruled until her death in the middle of the 10th century CE.

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.