Succession to the British throne is determined by descent, sex, legitimacy, and religion. Under common law, the Crown is inherited by a sovereign's children or by a childless sovereign's nearest collateral line. The Bill of Rights 1689 and the Act of Settlement 1701 restrict succession to the throne to the legitimate Protestant descendants of Sophia of Hanover who are in "communion with the Church of England". Spouses of Catholics were disqualified from 1689 until the law was amended in 2015. Protestant descendants of those excluded for being Roman Catholics are eligible.

Sophia was Electress of Hanover from 19 December 1692 until 23 January 1698 as the consort of Prince Elector Ernest Augustus. She was later the heiress presumptive to the thrones of England and Scotland and Ireland under the Act of Settlement 1701, as a granddaughter of King James VI and I. Sophia died less than two months before she would have become Queen of Great Britain and Ireland. Consequently, her son George I succeeded her first cousin once removed, Queen Anne, to the British throne, and the succession to the throne has since been defined as, and composed entirely of, her legitimate and Protestant descendants.