A queen regnant (plural: queens regnant) is a female monarch, equivalent in rank to a king, who reigns in her own right, in contrast to a queen consort, who is the wife of a reigning king, or a queen regent, who is the guardian of a child monarch reigning temporarily in their stead. An empress regnant is a female monarch who reigns in her own right over an empire.
A queen regnant possesses and exercises sovereign powers. A queen consort shares her husband's rank and titles, but does not share the sovereignty of her husband. The husband of a queen regnant traditionally does not share his wife's rank, title or sovereignty. However, the concept of a king consort is not unheard of in contemporary or classical periods.
A queen dowager is the widow of a king. A queen mother is a queen dowager who is also the mother of a reigning sovereign.
In Ancient Egypt, Ancient Persia, Asian and Pacific cultures, and even some European countries, as noted below, female monarchs have been given the title king or its equivalent, such as pharaoh, when gender is irrelevant to the office, or else have used the masculine form of the word in languages where gender is needed. The Byzantine Empress Irene sometimes called herself basileus (βασιλεύς), 'emperor', rather than basilissa (βασίλισσα), 'empress' and Jadwiga of Poland was crowned as Rex Poloniae, King of Poland.
Among the Davidic Monarchs of the Kingdom of Judah, there is mentioned a single queen regnant, Athaliah, though the Hebrew Bible regards her negatively as a usurper. The much later Hasmonean Queen Salome Alexandra (Shlom Tzion) was highly popular.
Accession of a regnant occurs as a nation's order of succession permits. Methods of succession to queendoms, kingdoms, tribal chiefships, and such include nomination when the sitting monarch or a council names an heir, primogeniture when the children of a monarch or chief become regents in order of birth from eldest to youngest, and ultimogeniture when the children become regents in the reverse order of birth from youngest to eldest. The scope of succession may be matrilineal, patrilineal, or both; or, rarely, open to general election when necessary. The right of succession may be open to men and women, or limited to men only or women only.
The most typical succession in European monarchies from the Late Middle Ages through most of the twentieth century was male-preference primogeniture; i.e., the order of succession cycled through the sons of the monarch in order of their birth, followed by the daughters or grandsons. Historically, many realms forbade succession by women or through a female line in obedience to the Salic law, and some still do. No queen regnant ever ruled France, for example. Only one woman, Maria Theresa, ruled Austria. As noted in the list below of widely known ruling queens, many ruled in European monarchies.
In the waning days of the 20th century and early days of the 21st, Sweden, Norway, Belgium, the Netherlands, Denmark, Luxembourg and the UK amended their acts of succession to absolute primogeniture. In some cases the change does not take effect during the lifetimes of people already in the line of succession at the time the law was passed.
In 2011, the 16 Realms of the Commonwealth agreed to remove the rule of male-preference primogeniture. Once the necessary legislation was passed, this means that had Prince William had a daughter first, a younger son would not become heir apparent.
In China, Wu Zetian became the Chinese empress regnant and established the Zhou Dynasty after dismissing her sons. It should be noted, however, that Empress Wu used the title huangdi (皇帝, "emperor") and in many European sources, as a female emperor rather than an empress regnant. Similarly, a few decades earlier in Korea, Queen Seondeok of Silla and Jindeok of Silla developed the term yeowang (여왕, "female king") to refer to themselves instead of the term wangbi (왕비), which is usually translated as "queen consort" and refers to the wife of a king or emperor.
Although the Chrysanthemum Throne of Japan is currently barred to women, this has not always been the case; throughout Japanese history there have been eight empresses regnant. Again, the Japanese language uses the term josei tennō (女性天皇, "female imperial ruler") for the position which would be "empress regnant" in English, with kōgō (皇后) being the term reserved for an empress consort.