United Kingdom of Great Britain and Ireland
The United Kingdom of Great Britain and Ireland was established by the Acts of Union in 1801 that united the Kingdom of Great Britain and the Kingdom of Ireland into one unitary and sovereign state. It continued in this form until 1927, when it evolved into the United Kingdom of Great Britain and Northern Ireland, after the Irish Free State gained a degree of independence in 1922.
Source: Wikipedia — United Kingdom of Great Britain and Ireland (CC BY-SA 4.0)