Partition of Ireland
The partition of Ireland () divided the island of Ireland into two distinct jurisdictions, Northern Ireland and Southern Ireland. It took place on 3 May 1921 under the Government of Ireland Act 1920. Today the former is still known as Northern Ireland and forms part of the United Kingdom, while the latter is now a sovereign state also named Ireland and sometimes called the Republic of Ireland.
Monarchy of the United Kingdom
In 1800, as a result of the Irish Rebellion of 1798, the Act of Union merged the kingdom of Great Britain and the kingdom of Ireland into the United Kingdom of Great Britain and Ireland. The whole island of Ireland continued to be a part of the United Kingdom until 1922, when what is now the Republic of Ireland won independence as the Irish Free State, a separate Dominion within the Commonwealth. The Irish Free State was renamed Éire (or "Ireland") in 1937, and in 1949 declared itself a republic, left the Commonwealth and severed all ties with the monarchy. Northern Ireland remained within the Union. In 1927, the United Kingdom changed its name to the United Kingdom of Great Britain and Northern Ireland, while the monarch's style for the next twenty years became "of Great Britain, Ireland and the British Dominions beyond the Seas, King, Defender of the Faith, Emperor of India".