A queen regnant (plural: queens regnant) is a female monarch who reigns in her own right, in contrast to a queen consort, who is the wife of a reigning king. An empress regnant is a female monarch who reigns in her own right over an empire.

A queen regnant possesses and exercises sovereign powers. The husband of a queen regnant does not usually share his wife's rank, title or sovereignty. A queen consort shares her husband's rank and titles, but does not share the sovereignty of her husband.

A queen dowager is the widow of a king who reigned in his own right. A queen mother is a queen dowager who is also the mother of a reigning sovereign.

In Ancient Egypt, Pacific cultures, and European countries, as noted below, women monarchs have been given the title king or its equivalent, such as pharaoh, when gender is irrelevant to the office. Also 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.

Juliana (Juliana Louise Emma Marie Wilhelmina; 30 April 1909 – 20 March 2004) was the Queen regnant of the Kingdom of the Netherlands between 1948 and 1980. She was the only child of Queen Wilhelmina and Prince Henry. She was married to Prince Bernhard of Lippe-Biesterfeld, with whom she had four children: Princess Beatrix (born 1938), Princess Irene (born 1939), Princess Margriet (born 1943), Princess Christina (born 1947). During the Second World War she lived in exile with her children in Ottawa, Canada. She became Queen of the Netherlands with her mother's abdication in 1948 and was succeeded by Queen Beatrix after her own abdication in 1980. During her reign both Indonesia (Dutch East Indies) proclaimed in 1945, but recognized in 1949 and Suriname in 1975 became independent from the Netherlands. Her birthday is celebrated annually as Koninginnedag, Queen's Day. Upon her death at the age of 94, she was the longest-lived former ruling monarch in the world. She is commemorated in space, in the name of the asteroid 816 Juliana.

Elizabeth II (Elizabeth Alexandra Mary; born 21 April 1926) is the constitutional monarch of 16 sovereign states known as the Commonwealth realms, and head of the 54-member Commonwealth of Nations. She is also head of state of the Crown Dependencies.

Elizabeth was born in London, and educated privately at home. Her father acceded to the throne as George VI in 1936 on the abdication of his brother Edward VIII. She began to undertake public duties during the Second World War, in which she served in the Auxiliary Territorial Service. On the death of her father in 1952, she became Head of the Commonwealth and queen regnant of seven independent Commonwealth countries: the United Kingdom, Canada, Australia, New Zealand, South Africa, Pakistan, and Ceylon. Her coronation service in 1953 was the first to be televised. Between 1956 and 1992, the number of her realms varied as territories gained independence and some realms became republics. Today, in addition to the first four aforementioned countries, Elizabeth is Queen of Jamaica, Barbados, the Bahamas, Grenada, Papua New Guinea, the Solomon Islands, Tuvalu, Saint Lucia, Saint Vincent and the Grenadines, Belize, Antigua and Barbuda, and Saint Kitts and Nevis.

Wilhelmina (Wilhelmina Helena Pauline Maria; 31 August 1880 – 28 November 1962) was Queen regnant of the Kingdom of the Netherlands from 1890 to 1948. She reigned for nearly 58 years, longer than any other Dutch monarch. Her reign saw World War I and World War II, the economic crisis of 1933, and the decline of the Netherlands as a major colonial power. Outside the Netherlands she is primarily remembered for her role in World War II, in which she proved to be a great inspiration to the Dutch resistance.

Princess Wilhelmina Helena Pauline Maria of the Netherlands, Princess of Orange-Nassau, was born on 31 August 1880 in The Hague, Netherlands. She was the only child of King William III and his second wife, Emma of Waldeck and Pyrmont. Her childhood was characterised by a close relationship with her parents, especially with her father, who was 63 years of age when she was born.

King William III had three sons with his first wife, Sophie of Württemberg. However, when Wilhelmina was born, William had already outlived two of them and only the childless Prince Alexander and the King's uncle Prince Frederick of the Netherlands were alive, so under the Semi-Salic system of inheritance that was in place in the Netherlands until 1887, she was third in line to the throne from birth. When Prince Frederick died a year later in 1881, she became second in line. When Wilhelmina was four, Alexander died and the young girl became heiress presumptive.

The Queen of Sheba (Hebrew: מלכת שבא‎, Malkaṯ Šəḇâ in Biblical Hebrew; Malkat Sh'va in Modern Hebrew; Ge'ez: ንግሥተ ሳባ, Nigiste Saba (Nəgəstä Saba); Arabic: ملكة سبأ‎, Malikat Sabaʾ) was a monarch of the ancient kingdom of Sheba and is referred to in Ethiopian history, the Bible, the Qur'an, Yoruba customary tradition, and Josephus. She is widely assumed to have been a queen regnant, although there is no historical proof of this; in fact, she may have been a queen consort. The location of her kingdom is believed to have been in Ethiopia and Yemen.

The queen of Sheba has been called a variety of names by different peoples in different times. To King Solomon of Israel she was the Queen of Sheba. In Islamic tradition she was called Bilqis or Balqis by the Arabs, who say she came from the city of Sheba, also called Mareb, in Yemen or Arabia Felix. The Roman historian Josephus calls her Nicaule. The Ethiopian people claim her as Makeda or Maqueda. She is thought to have been born sometime in the 10th century BC. Her lineage was part of the Ethiopian dynasty established in 1370 BCE by Za Besi Angabo, which lasted 350 years; Makeda's grandfather and father were the last two rulers of this dynasty. Makeda's mother was known as Queen Ismenie. In 1005 BCE, Makeda's father appointed her as his successor from his deathbed.