Elizabeth II (Elizabeth Alexandra Mary; born 21 April 1926) is the Queen regnant of sixteen independent states and their overseas territories and dependencies. Though she holds each crown and title separately and equally, she is resident in and most directly involved with the United Kingdom, her oldest realm, over parts of whose territories her ancestors have reigned for more than a thousand years. She ascended the thrones of seven countries in February 1952 (see Context below).

In addition to the United Kingdom, Elizabeth II is also Queen of Canada, Australia, New Zealand, Jamaica, Barbados, the Bahamas, Grenada, Papua New Guinea, the Solomon Islands, Tuvalu, Saint Lucia, Saint Vincent and the Grenadines, Antigua and Barbuda, Belize, and Saint Kitts and Nevis, in each of which she is represented by a Governor-General. The 16 countries of which she is Queen are known as Commonwealth realms, and their combined population, including dependencies is over 129 million. In theory her powers are vast; in practice (and in accordance with convention) she herself never intervenes in political matters. In the United Kingdom at least, however, she is known to take an active behind-the-scenes interest in the affairs of state, meeting regularly to establish a working relationship with her government ministers.

Elizabeth II holds a variety of other positions, among them Head of the Commonwealth, Supreme Governor of the Church of England, Duke of Normandy, Lord of Mann , and Paramount Chief of Fiji. Her long reign has seen sweeping changes in her realms and the world at large, perhaps most notably the dissolution of the British Empire (a process that began in the last years of her father's reign) and the consequent evolution of the modern Commonwealth of Nations.

Since 1947, the Queen has been married to Prince Philip, Duke of Edinburgh, born a prince of Greece and Denmark but after naturalisation known as Philip Mountbatten and subsequently created Duke of Edinburgh. To date the couple have four children and eight grandchildren; the eighth (Viscount Severn) was born on 17 December 2007 to Prince Edward and Sophie, Countess of Wessex.