Elizabeth II was Queen of the United Kingdom and other Commonwealth realms from 6 February 1952 until her death in 2022. She was queen regnant of 32 sovereign states over the course of her lifetime and remained the monarch of 15 realms by the time of her death. Her reign of 70 years and 214 days is the longest of any British monarch or female monarch, and the second longest verified reign of any monarch of a sovereign state in history.

The monarchy of the United Kingdom, commonly referred to as the British monarchy, is the form of government used by the United Kingdom by which a hereditary monarch reigns as the head of state, with their powers regulated by the British Constitution. The term may also refer to the role of the royal family within the UK's broader political structure. The current monarch is King Charles III, who ascended the throne on 8 September 2022, upon the death of his mother, Queen Elizabeth II.