Elizabeth II Queen Head of the Commonwealth and Queen regnant of seven independent Commonwealth countries: the United Kingdom, Canada, Australia, New Zealand, South Africa, Pakistan, and Ceylon.

 Elizabeth II ( born 21 April 1926) is Queen of the United Kingdom and fifteen other Commonwealth realms.[b]

Elizabeth was born in Mayfair, London, as the first child of the Duke and Duchess of York (later King George VI and Queen Elizabeth). Her father ascended the throne in 1936 upon the abdication of his brother, King Edward VIII, making Elizabeth the heir presumptive. She was educated privately at home and began to undertake public duties during the Second World War, serving in the Auxiliary Territorial Service. In November 1947, she married Philip, Duke of Edinburgh, a former prince of Greece and Denmark, with whom she had four children: Charles, Prince of Wales; Anne, Princess Royal; Prince Andrew, Duke of York; and Prince Edward, Earl of Wessex.

When her father died in February 1952, Elizabeth – then 25 years old – 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. She has reigned as a constitutional monarch through major political changes, such as the Troubles, devolution in the United Kingdom, accession of the United Kingdom to the European Communities, the United Kingdom's withdrawal from the European Union, Canadian patriation, and the decolonisation of Africa. Between 1956 and 1992, the number of her realms varied as territories gained independence, and as realms, including South Africa, Pakistan, and Ceylon (renamed Sri Lanka), became republics. Her many visits and meetings include a state visit to the Republic of Ireland and visits to or from five popes. Significant events have included her coronation in 1953 and the celebrations of her Silver, Golden, and Diamond Jubilees in 1977, 2002, and 2012, respectively. In 2017, she became the first British monarch to reach a Sapphire Jubilee. On 9 April 2021, after over 73 years of marriage, her husband Prince Philip died at the age of 99.

Elizabeth is the longest-lived and longest-reigning British monarch, the longest-serving female head of state in world history, the world's oldest living monarch, longest-reigning current monarch, and oldest and longest-serving current head of state. Elizabeth has faced republican sentiment and press criticism of the royal family, particularly after the breakdown of her children's marriages, her annus horribilis in 1992, and the 1997 death of her former daughter-in-law Diana, Princess of Wales. However, support for the monarchy in the United Kingdom has been and remains consistently high, as does her personal popularity.