A crown prince or crown princess is the heir apparent to the throne in a royal or imperial monarchy. The wife of a crown prince is also styled crown princess. An heir presumptive, by contrast, is someone who is first in line to inherit a title but who can be displaced by the birth of a more eligible heir.

Crown prince is not used as a title in monarchies wherein the hereditary sovereign holds a title below that of king/queen (such as grand duke or prince), although it is sometimes used as a synonym for heir apparent.

In Europe, where primogeniture governs succession to all monarchies except those of the Papacy and Andorra, the eldest son or (more recently) eldest child of the current monarch fills the role of crown prince or princess, depending upon whether females of the dynasty enjoy personal succession rights. The eldest living child of a monarch is sometimes not the heir apparent or crown prince, because that position can be held by a descendant of a deceased older child who, by "right of representation", inherits the same place in the line of succession that would be held by the ancestor if he or she were still living (for example, Carl Gustaf, Duke of Jämtland was the crown prince of Sweden from 1950 to 1973, as the senior grandson by male primogeniture of King Gustaf VI Adolf of Sweden, although the former Prince Sigvard, Duke of Uppland was Gustaf VI Adolf's eldest living son, and Prince Bertil, Duke of Halland his eldest living dynastic son during those years).

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