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 titled crown princess.
The term is now borne as a title mainly in Asia, Scandinavia, and the Middle East; but it may also be used generically to refer to the person or position of the heir apparent in other kingdoms. However, heirs apparent to non-imperial and non-royal monarchies (i.e., wherein the hereditary sovereign holds a title below that of king/queen, e.g., grand duke or prince), crown prince is not used as a title, 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 (Spain) or eldest child (Belgium, Denmark, the Netherlands, Norway, Sweden, and the United Kingdom) 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 (e.g., Carl Gustaf, Duke of Jämtland, was 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).
Taizi (Chinese: 太子, p tàizǐ, lit. "Supreme Son") was the title of the crown prince of imperial China.
Traditional Confucian political theory favored strict agnatic primogeniture, with younger sons displaying filial obedience to the eldest upon the passing of the father. This rather straightforward system was somewhat complicated by polygamy: since later wives were subordinated to the first, their children – even when born first – were likewise subordinated to hers.
Following Lu Gu's conversion of Liu Bang to Confucianism in the early 1st century BC, Chinese dynasties have observed it in theory though not always in practice. Liu Bang himself began to favor a later concubine to his primary empress and doubt the competence of his heir Liu Ying. Even worse conflicts could occur when invaders – previously observing their own rules of inheritance – began to Sinify, as happened to the 10th-century Liao dynasty.
Under the Ming Dynasty, the traditional Confucian principles of succession were upheld by the Hongwu Emperor's Instructions of the Ancestor of the August Ming. These presented a grave problem when his eldest son died early, leaving a power struggle between a sheltered teenage grandson and his many experienced and well-armed uncles. One of these, the Prince of Yan, eventually overthrew his nephew under the pretense of saving him from ill counsel. His own legitimacy was precariously established: a charred body was procured from the ruins of Nanjing and proclaimed to be the accidentally-killed emperor; the nephew's reign was then condemned and delegitimized and the surviving son kept imprisoned and single; and imperial records were falsified to establish the Prince of Yan as his father's favorite and as a son of the primary wife, giving him primacy over his other brothers.
Crown Prince Dan (Chinese: 太子丹; pinyin: Tàizǐ Dān) was a crown prince of the State of Yan during the Warring States period of ancient China. He was also called Yan Dan (Chinese: 燕丹; pinyin: Yān Dān).
He lived in the State of Qin as a hostage, but returned to Yan in 232 BC. He sent Jing Ke to assassinate King Zheng of Qin, who later assumed the title Qin Shi Huang and became the first Emperor of China, but Jing failed. King Xi of Yan, Dan's father and the last king of Yan, ordered the execution of Dan to please Qin after the Yan capital Ji fell to Qin. Invasion of Qin did halt for few years, during which time the states of Wei and Chu were conquered. Meanwhile, the King Xi of Yan moved to the Liaodong Commandery.
The state of Yan was conquered in 222 BC and King Xi was captured.
All except King Xi were featured in the Chinese period epic The Emperor and the Assassin. Prince Dan is also featured in the 2004 TV series Assassinator Jing Ke.