The Act of Succession of 27 March 1953 ( da, tronfølgeloven) was adopted after a 1953 referendum in

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Danish Realm, Kingdom of 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 older or younger brothers, a system known as male-preference cognatic preference

primogeniture Primogeniture ( ) is the right, by law or custom, of the firstborn legitimate child to inherit the parent's entire or main estate in preference to shared inheritance among all or some children, any illegitimate child or any collateral relativ ...

.http://sekr.uvm.dk/historie/tekster_tidssoejle/tid_hist/dan_16_grundlov_53.html
As the reigning

King Frederick IX Frederick IX ( da, Christian Frederik Franz Michael Carl Valdemar Georg; 11 March 1899 – 14 January 1972) was King of Denmark from 1947 to 1972. Born into the House of Glücksburg, Frederick was the elder son of King Christian X and Queen ...

had three daughters and no sons, this meant that Princess Margrethe became the

heir presumptive An heir presumptive is the person entitled to inherit a throne, peerage, or other hereditary honour, but whose position can be displaced by the birth of an heir apparent or a new heir presumptive with a better claim to the position in question. ...

instead of her uncle

Prince Knud 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 Christian X of Denmark, King Christian X and Alexandrine of Mecklenburg-Schw ...

. As Frederick IX's wife

Queen Ingrid Ingrid of Sweden (born: Princess Ingrid Victoria Sofia Louise Margareta of Sweden; 28 March 1910 – 7 November 2000) was Queen of Denmark from 1947 until 1972 as the wife of King Frederick IX. Born into the House of Bernadotte, she was the daug ...

was not expected to (and in fact did not) have any more children, this effectively ensured that Princess Margrethe would become

Queen of Denmark The monarchy of Denmark is a constitutional institution and a historic 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 alr ...

, which she did. The act also removed the succession rights of minor members of the House of Glücksburg such as

Prince Philip of Greece and Denmark Prince Philip, Duke of Edinburgh (born Prince Philip of Greece and Denmark, later Philip Mountbatten; 10 June 1921 – 9 April 2021) was the husband of Queen Elizabeth II. As such, he served as the consort of the British monarch from El ...

and his descendants. Following a referendum in 2009 the Act of Succession was amended so that primogeniture no longer puts males over females. In other words, the first-born child would become heir to the throne regardless of the child's sex. 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 actual line of succession at that time, but it does affect the current (as of 2018) line of succession: it puts Princess Isabella ahead of her younger brother Prince Vincent (who was born in the year 2011).

Notes

Law of Denmark Succession acts 1953 in Denmark {{Denmark-hist-stub