To honour the occasion, HELLO! Online has compiled a list of ten facts you may not have known about the Danish monarch.
Queen Margrethe II of Denmark
1. Margrethe was born on 16 April 1940 at the Amalienborg Palace in Copenhagen as the first child of parents Crown Prince Frederik and Crown Princess Ingrid of Denmark. Upon birth she was styled as "Her Royal Highness Princess Margrethe".
2. At the time of her birth, only males could ascend to the Danish throne, however in March 1953 a new Act of Succession was passed which meant females could become Queen as long as they did not have a brother. So at the age of 13, the young Princess became heiress presumptive to the throne.
Queen Margrethe II on her 18th birthday
3. In June 1967, millions across Denmark celebrated as the then Princess Margrethe married French diplomat Count Henri de Laborde de Monpezat. The new royal couple quickly became popular and Count Henri was given the style and title of "His Royal Highness Prince Henrik of Denmark".
4. A year later after their nuptials, in May 1968, the couple welcomed their first child Prince Frederik. Magrethe then gave birth to the couple's second child, Prince Joachim, in June 1969.
Princess Margrethe with her father King Frederik IX of Denmark before her wedding
5. On 14 January 1972, Margrethe succeeded the throne after her father King Frederik IX's passing. She became the first female monarch of Denmark since Margrethe I who ruled the Scandinavian countries in 1375-1412.
6. Margrethe is very close to Britain's Queen Elizabeth II and speaking in 2012 she revealed how she had always "admired" her and that she has helped influence herself as a Queen after watching how dedicated Elizabeth is to her nation.
Princess Margrethe and her husband Prince Henrik with their children Princes Frederik and Joachim
7. In January 2012, Queen Margrethe celebrated her Ruby Jubilee marking 40 years on the Danish throne. This was honoured with events across Denmark including a carriage procession.
8. In her spare time, the Danish monarch enjoys painting and over the years she has held many art shows. Her illustrations were used for the Danish edition of The Lord of the Rings, under the pseudonym Ingahild Grathmer, after she sent them to J.R.R. Tolkien who was instantly impressed by the royal's drawings.
Queen Margrethe II and Prince Henrik of Denmark
9. The Danish royal has been applauded for her sense of style over the years and in March 2013, The Guardian named her as one of the fifty best-dressed over 50s in the world.
10. Margrethe has been credited with maintaining the public's faith and admiration for the Danish Royal Family and the loved Queen often scores very high approval ratings with members of the public in Denmark.