Ireland, also commonly referred to as the Republic of Ireland, is a sovereign state in Europe occupying about five-sixths of the island of Ireland. The capital and largest city is Dublin, located in the eastern part of the island, whose metropolitan area is home to around a quarter of the country's 4.6 million inhabitants. The state shares its only land border with Northern Ireland, a part of the United Kingdom. It is surrounded by the Atlantic Ocean, with the Celtic Sea to the south, Saint George's Channel to the south east, and the Irish Sea to the east. It is a unitary, parliamentary republic with an elected president serving as head of state. The head of government, the Taoiseach, is nominated by the lower house of parliament, Dáil Éireann.
Following the Irish War of Independence and the subsequent Anglo-Irish Treaty, Ireland gained effective independence from the United Kingdom as the Irish Free State in 1922. Northern Ireland exercised an option called the Ulster Month to remain in the United Kingdom. Initially a dominion within the British Empire, the Free State received official British recognition of full legislative independence in the Statute of Westminster of 1931.