Frederik IX of Denmark in the context of "Henri de Laborde de Monpezat"

The Act of Succession of 27 March 1953 (Danish: tronfølgeloven) is an act adopted after a 1953 referendum in Denmark and dictates the rules governing the succession to the Danish throne. The 1953 referendum changed the act so that it became possible for a woman to inherit the throne if she has no brothers, a system known as male-preference cognatic preference primogeniture. As the reigning King Frederik IX had three daughters and no sons, this made Princess Margrethe heiress presumptive to the throne, replacing her uncle Prince Knud. As Frederik IX's wife Queen Ingrid was not expected to (and did not) have any more children, this effectively ensured that Princess Margrethe would become Queen of Denmark, which she did in 1972. The act also removed the succession rights of minor members of the House of Glücksburg.

Following a referendum in 2009, the Act of Succession was amended so that primogeniture no longer puts males over females, meaning the first-born child would become heir apparent to the throne regardless of gender. The expected result of the referendum was on the balance, since 40% of the entire electorate had to vote yes in order to make the change. However, the succession amendment was confirmed by a larger turnout especially in rural areas. The change of the act had no effect on the expected line of succession at the time, but would affect the line of succession among the then Crown Prince Frederick's younger children, putting Princess Isabella (who was born in 2007) ahead of her younger brother Prince Vincent (born in 2011).

The wedding of Constantine II, King of the Hellenes, and Princess Anne-Marie of Denmark took place on Friday, 18 September 1964, at the Metropolitan Cathedral of Athens.

Constantine II was the reigning Greek monarch, while Princess Anne-Marie was the youngest daughter of King Frederik IX and Queen Ingrid of Denmark. It was the second, and to date, the last wedding of a reigning Greek monarch, and the first to be held in Greece.

Knud, Hereditary Prince of Denmark (Knud Christian Frederik Michael; 27 July 1900 – 14 June 1976) was a member of the Danish royal family, the younger son and child of King Christian X and Queen Alexandrine.

From 1947 to 1953, he was heir presumptive to his older brother, King Frederik IX, and would have succeeded him as king following his death in January 1972 had it not been for a change in the Danish Act of Succession that replaced him with his niece, Queen Margrethe II. Later, Knud's two sons, Ingolf and Christian, were stripped of their titles of prince and removed from the line of succession by the new law because they had married commoners without asking consent from their uncle.