Mountbatten-Windsor is the personal surname used by some of the male-line descendants of Queen Elizabeth II and Prince Philip, Duke of Edinburgh. Under a declaration made in Privy Council in 1960, the name Mountbatten-Windsor applies to male-line descendants of Queen Elizabeth II without royal styles and titles. Individuals with royal styles do not usually use a surname, but some descendants of the Queen with royal styles have used Mountbatten-Windsor when a surname was required.

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.