The island of Ireland is divided between two sovereign states: the Republic of Ireland, which spans across five sixths of the island's area, and the United Kingdom, which takes up the remaining sixth part. The UK's part is commonly known as Northern Ireland. Irish nationalism believes this division to be illegitimate, and demands the unification of the whole territory under one single sovereign state.
The current territory of the Republic of Ireland is independent from the UK since 1922, when it was was proclaimed as the Irish Free State, with the British monarch as its head of state. Since 1937 de facto, and since 1948 de iure, the country has been a republic.
Northern Ireland remained in the UK in 1922. Since 1999, one year after the Good Friday Agreements were signed, Northern Ireland has enjoyed legislative and executive devolved powers. The Good Friday Agreements recognize the right of the people of Northern Ireland to decide whether the territory should remain a part of the UK, or rather re-unify with the rest of Ireland. The Agreements further specify that, should the people of the Republic of Ireland and of Northern Ireland —each one separately— decide to reunify the island, the Irish and UK governments would be legally bound to give effect to that wish. The possibility of independence of Northern Ireland alone is not foreseen in the text.
Besides this, Northern Ireland and the Republic of Ireland —since 1999 too— share a series of governing bodies under the umbrella of the North/South Ministerial Council, which are responsible for powers on an all-Ireland basis, which include tourism, education, agriculture, environment, health, water, language, trade and transport.
The Good Friday Agreement also provide for the birth right of every Northern Irish person to be recognized and accepted either as British, Irish or both. This includes the right to hold a UK passport, a Republic of Ireland passport, or both.
The identity breakup of the population of Northern Ireland is a complex one, according to the 2011 census —the first one in which a question on national identity was included. Results (more than one option could be chosen) were as follows: British 48.4%; Northern Irish 29.4%; Irish 28.4%; other options 5%. Generally speaking, Catholics tended to define themselves as Irish while Protestants tended to define themselves as British. Nevertheless, this was in now way an automatic correlation. And thus, for example, both Catholics and Protestants identified themselves as Northern Irish in similar proportions.