The Danish Act of Succession,^[1] adopted on 5 June 1953, restricts the throne to those descended from Christian X and his wife, Alexandrine of Mecklenburg-Schwerin, through approved marriages. By a change in the law in 2009, succession is governed by absolute primogeniture.^[2]

Dynasts lose their right to the throne if they marry without the permission of the monarch, to be given in the Council of State. Individuals born to unmarried dynasts or to former dynasts who married without royal permission, and their descendants, are excluded from the throne. Further, when approving a marriage, the monarch can impose conditions that must be met in order for any resulting offspring to have succession rights. If there is no eligible person(s) to inherit the throne, the Danish Parliament (the Folketing) has the right to elect a new monarch and determine a line of succession.

People in the line of succession are listed with a number signifying their place in the line.

From the London Protocol in 1852 till 1953, various male-line descendants of King Christian IX had succession rights in Denmark except King George I of Greece (former Prince William of Denmark) and subsequent Kings of Greece, whose rights to the Danish throne were blocked by Article VI of the 1863 treaty between Denmark, France, the United Kingdom and Russia recognising George I as King of the Hellenes (Article VI stated: In no case shall the Crown of Greece and the Crown of Denmark be united on the same head.),^[15] although King George I never renounced his rights to the Danish throne when he assumed the Greek one, though he did defer his succession rights and agreed that his younger brother's would supersede his.^[16]

King Haakon VII of Norway (former Prince Carl of Denmark) whose rights was blocked by Section XI of the Constitution of Norway which states The king must not receive any other crown or government without the Storting's consent, for which two-thirds of the votes are required, from 19 August 1908.^[17]

The new Act of Succession terminated succession rights but left the excluded individuals in possession of their titles. This created a class of people with royal titles but no rights to the throne. As a distinction, those entitled to inherit the throne are called "Prins til Danmark" (Prince to Denmark, although this distinction is not made in English) while those without succession rights are referred to as "Prins af Danmark" (Prince of Denmark).

From 1853 until 1953, the Crown passed according to agnatic primogeniture. The monarch in 1953, King Frederik IX, had three daughters but no sons. Before the 1953 Act, the heir presumptive to the throne was Hereditary Prince Knud, the King's younger brother. The Hereditary Prince was far less popular than the King was. Further, his mother-in-law, Princess Helena, was accused of supporting the Nazi movement during the Second World War. These factors, combined with a belief that the Salic law was outdated, resulted in the movement to change the succession law so that Frederick's eldest daughter, the then Princess Margrethe, could inherit the throne. Thus, the Salic law was changed to male-preference primogeniture in 1953, meaning that females could inherit, but only if they had no brothers.

Prince Knud had three children. His sons married without the monarch's permission and lost both their royal titles and succession rights. Only Knud's daughter, the unmarried Princess Elisabeth, retained her rights to the throne. Since her death, the line of succession has consisted only of descendants of King Frederik IX.

Queen Margrethe II's youngest sister, Anne-Marie, married King Constantine II of Greece in 1964. As she was marrying a foreign ruler, although he was himself a prince of Denmark, consent to the marriage was given on the condition that Anne-Marie renounced her and her descendants' rights to the Danish throne.^[14]

In 2008, the Danish parliament voted in favour of instituting absolute primogeniture, which would make the Danish monarch's first-born child heir apparent regardless of gender, similar to Sweden and Norway. The bill was voted through two successive parliaments, and submitted to a referendum. The change in succession law did not affect the immediate line of succession as all of Margrethe II's descendants would hold the same positions under both laws.^[18][19] Crown Prince Frederik and Crown Princess Mary became parents to twins born on 8 January 2011. Upon their birth, the twins assumed the fourth and fifth place in the line of succession, according to the absolute primogeniture principle adopted, thereby not giving Prince Vincent precedence over his older sister Princess Isabella.^[20]

In 2022, Queen Margrethe II stripped the children of her son Prince Joachim of their princely titles, though they remain in the line of succession (see Count of Monpezat#2023 style changes for details).

• Danish royal family tree