In 2017, Margrethe II celebrated 45 years as the monarch of which country?

Margrethe II is the Queen of Denmark, as well as the supreme authority of the Church of Denmark and Commander-in-Chief of the Danish Defence. Born into the House of Glücksburg, a royal house with origins in Northern Germany, she was the eldest child of Frederick IX of Denmark and Ingrid of Sweden. She became heir presumptive to her father in 1953 when a constitutional amendment allowed women to inherit the throne.

Margrethe succeeded her father upon his death on 14 January 1972. On her accession, she became the first female monarch of Denmark since Margrethe I, ruler of the Scandinavian kingdoms in 1375–1412 during the Kalmar Union. In 1967, she married Henri de Laborde de Monpezat, with whom she has two sons: Crown Prince Frederik and Prince Joachim. She celebrated 45 years of being on the Danish throne in 2017. Margrethe is the second-longest-reigning Danish monarch after her ancestor Christian IV.