A queen consort is the title given to the wife of a reigning king. Queens consort usually share their husbands' rank (in salic or semi-salic law monarchies) and hold the feminine equivalent of their husbands' monarchical titles. Most of the time, however, they have no real power.
Most queens in history were Queen consort - the other kind, queens regnant in their own right who had inherited the throne on the death of the previous monarch being far fewer in numbers. In some countries, the Order of succession laws completely excluded women from taking the throne. Even where women could at all become monarchs, the law gave a clear preference to male inheritors (for example, on the death of Henry VIII in England, the throne was given to his child son Edward VI rather than to Edward's older sisters. Only due to Edward's dying without issue did these sisters, Mary I and Elizabeth I get the chance to become queens.
The wife of a reigning king is called a queen consort. By contrast, the husband of a reigning queen is usually not called "king consort", although it was more common in Europe's past for husbands of queens regnant to take the title of king (e.g. Francisco de Asis of Bourbon-Cadiz in Spain, Philip II of Spain in England, Antoine of Bourbon-Vendôme in Navarre and King Consort Ferdinand of Portugal). Rather, he is normally called a prince or prince consort, as with the husbands of Queen Victoria and Queen Elizabeth II.
Where some title other than that of king is held by the sovereign, his wife is referred to by the feminine equivalent, such as empress consort or princess consort. In monarchies where polygamy has been practiced (such as Morocco, Thailand) or is still practiced (such as the Zulu nation) none or only some of the wives of the king may bear the title of queen. In Morocco, no king's wife enjoys a queenly title, although the present king Mohammed VI has broken with tradition and given his wife Lalla Salma the title of princess. In Thailand, traditionally a wife of the king only became queen if she was of royal birth herself (a practice also common in Europe until well into the 20th century), and there are several gradations of the queenly title to which a consort can be elevated. Among the Zulus, although all of the king's wives are accorded the title queen and the style of Royal Highness, only the "Great Wife" is considered the queen consort.
In general, the consorts of monarchs have no power per se, even when their position is constitutionally or statutorily recognized. However, often the queen consort of a deceased king (the queen dowager or queen mother) has served as regent while her child, the successor to the throne, was still a minor - for example:
Besides these examples, there have been many cases of queens consort being shrewd or ambitious stateswomen and, albeit unofficially, being among the King's major advisors. In some cases, the queen consort has been the chief power behind her husband's throne; e.g. Maria Luisa of Parma, wife of Carlos IV of Spain, and Alexandra Fyodorovna (Alix of Hesse), wife and Empress Consort of Nicholas II of Russia.
A potential exception to the rule of referring to the wife of the monarch as queen consort may be Camilla, Duchess of Cornwall, spouse of Charles, Prince of Wales. When their wedding was announced it was declared that, in the event of Charles's ascent to the British throne, Camilla would assume the title of Princess Consort and not that of Queen. Subsequent British ministerial comment during Parliamentary discussion confirmed, however, that she would necessarily retain the legal prerogatives reserved for, and the legal title of, a British queen consort. In the other Realms such as Australia, Canada and New Zealand, there is no constitutional position as queen consort. It is merely a courtesy title.
There are a few cases in which a married couple has ruled a kingdom jointly.
Ferdinand II of Aragon and his wife Isabella, a queen in her own right, Isabella I of Castile, ruled their kingdoms as one dominion. Ferdinand was also called Ferdinand V of Castile. However, the two kingdoms would not be legally united until the monarchs' grandson Charles V, Holy Roman Emperor, acceded to both thrones as Charles I of Spain.
The joint reign of William III and Mary II of England resulted from a unique and extra-legal change by the Parliament of England to the law of succession. When Mary, the Protestant daughter and heiress presumptive of James II, was displaced in the order of succession by the birth of a son to his Catholic queen consort, Protestant fears were provoked.
Mary's husband, William of Orange, Stadtholder of the Protestant Dutch Republic and also a descendant of James I, was invited by the leaders of Parliament to ascend the throne of his deposed father-in-law. After James II fled the country, Parliament offered the crown to William and Mary jointly.
The couple remained childless, and William ruled alone after Mary's death in 1694. The future Queen Anne's claims had been deferred by Parliament until his death.
Past queens consort:
See Royal Consorts of the United Kingdom and its predecessor realms for a more complete list of queens consort of the United Kingdom.
Present queens consort:
Because queens consort lack an ordinal with which to distinguish between them, many historical texts and encyclopedias refer to deceased consorts by their pre-marital or maiden name or title, not by their marital royal title.