Ireland is of this world.
Ireland ( [ ˈaɪərlənd ] Éire [ ˈeːɾʲə ] ; Ulster-Scots : Airlann [ - scoˈɑːrlən ] ) is an island in the North Atlantic . Ireland is the second-largest island of the British Isles , the third-largest in Europe , and the twentieth-largest on Earth . Just under 4.6 million live in the Republic of Ireland and just over 1.8 million live in Northern Ireland . With the Acts of Union in 1801 , Ireland became a part of the United Kingdom .