Princess Royal is a style customarily (but not automatically) awarded by a Britishmonarch to his or her oldest daughter. The style is held for life, so a princess cannot be given the style during the lifetime of another Princess Royal. There have been seven Princesses Royal in total [1] (http://www.heraldica.org/faqs/britfaq#p2-34).
The following is a complete list of women officially styled as "Princess Royal":-
Princess Mary[?] (1631 - 1660): daughter of King Charles I; wife of Willem II, Prince of Orange (1626 - 1650)
Princess Anne[?] (1709 - 1759): daughter of King George II; wife of Willem IV, Prince of Orange (1711 - 1751)
Princess Charlotte[?] (1766 - 1828): daughter of King George III; wife of Friedrich I, King of Württemberg (1754 - 1816)
Princess Victoria (1840 - 1901): daughter of Queen Victoria and Prince Albert; wife of Friedrich III, King of Prussia and German Emperor (1831 - 1888); mother of Wilhelm II, last King of Prussia and last German Emperor (1859 - 1941)
... (162)
Charles C. Pinckney[?]
14
Federalist
Rufus King (14)
Other elections: 1792, 1796, 1800, 1804, 1808, 1812, 1816
Source: U.S. Office of the Federal ...