- His Royal Highness redirects here. For the 1932 Australian film, see His Royal Highness (1932 film). For the 1981 comedy play, see Her Royal Highness..? (play)
Royal Highness (abbreviation HRH) is a style used to address or refer to some members of royal families, usually princes other than monarchs and their female consorts (i.e., kings and queens). When used as a direct form of address, spoken or written, it takes the form "Your Royal Highness". When used as a third person reference, it is gender-specific (Her Royal Highness or His Royal Highness, both abbreviated HRH) and, in plural, Their Royal Highnesses (TRH).
By the 17th century, all local rulers in Italy adopted the style Highness, that was once used by kings and emperors only. According to Denis Diderot's Encyclopédie, the style of Royal Highness was created on the insistence of Archduke Ferdinand of Austria, Cardinal-Infante of Spain, a younger son of King Philip III of Spain. The Archduke was travelling through Italy on his way to the Low Countries and, upon meeting Victor Amadeus I, Duke of Savoy, refused to address him as Highness unless the Duke addressed him as Royal Highness. Thus, the first use of the style Royal Highness was recorded in 1633. Gaston, Duke of Orléans, younger son of King Henry IV of France, encountered the style in Brussels and assumed it himself. His children later used the style, considering it their prerogative as grandchildren of France.
By the 18th century, Royal Highness had become the prevalent style for members of a continental reigning dynasty whose head bore the hereditary title of king or queen. The titles of family members of non-hereditary rulers (e.g., the Holy Roman Emperor, King of Poland, Princes of Moldavia and Wallachia -- and even the kin of the Princes of Orange who held hereditary leadership though not monarchical position in much of the Netherlands, etc.) were less clear, varying until rendered moot in the 19th century. After dissolution of the Holy Roman Empire in 1806, several of Germany's prince-electors and other now sovereign rulers assumed the title of grand duke and with it, for themselves, their eldest sons and consorts, the style of Royal Highness (Baden, Hesse, Mecklenburg, Saxe-Weimar).
African usage 
The vast majority of African royalty that make use of titles such as prince, chief and sheik, eschew the attendant styles that one would ordinarily be accustomed to seeing or hearing in accompaniment. Even in the cases of the aforesaid titles, they usually only exist as courtesies and may or may not have been recognised by a reigning fons honorum. However, some traditional leaders and their family members use royal styles when acting in their official roles as representatives of sovereign or constituent states, distinguishing their status from others who may use or claim traditional titles. For example, the Nigerian traditional rulers of the Yoruba are usually styled using the HRH The X of Y method, even though they are confusingly known as kings in English and not the princes that the HRH style usually suggests. The chiefly appellation Kabiyesi (lit. He (or She) whose words are beyond question) is likewise used as the equivalent of the HRH and other such styles by this class of royals when rendering their full titles in the Yoruba language. Furthermore, the wives of the king of the Zulu peoples, although all entitled to the title of "queen", do not share their husband's style of Majesty but instead are each addressed as "Royal Highness", with the possible exception of the Great Wife.
United Kingdom 
In the British monarchy the style of Royal Highness is associated with the rank of prince or princess (although this has not always applied, the notable exception being Prince Philip, Duke of Edinburgh, who was given the style of HRH in 1947 but was not created a prince until 1957). This is especially important when a prince has another title such as Duke (or a princess the title of Duchess) by which he or she would usually be addressed. For instance HRH The Duke of Connaught was a prince and a member of the royal family while His Grace The Duke of Devonshire is a non-royal duke and not a member of the British Royal Family. During the Diamond Jubilee celebrations the Queen was addressed as Her Royal Highness and this was seen as incorrect.
In the United Kingdom, letters patent dated 21 August 1996 stated that a style received by the spouse of a member of the Royal Family on their marriage ceased in the event of their divorce. It was for this reason that when TRH The Prince and Princess of Wales divorced, she ceased to be Royal Highness, and was styled Diana, Princess of Wales (although entitled to the prefix of "Lady" in her own right, she never reverted to its use). Similarly, HRH The Duchess of York was restyled Sarah, Duchess of York after her divorce from HRH The Duke of York.
In contradiction to other European kingdoms, the kingdom of Denmark reserves the superior style of Royal Highness only to the children of the monarch and the children of the crown prince; other grandchildren of a Danish monarch enjoy the style of Highness, e.g. Princess Elisabeth of Denmark.
See also 
- British prince
- Forms of address in the United Kingdom
- Royal and noble styles
- Table of Ranks (Russian)
- Use of courtesy titles and honorifics in professional writing