Ireland is an isle.
Ireland . Ireland is the second-largest island of the British Isles , the third-largest in Europe , and the twentieth-largest on Earth . Politically , Ireland is divided between the Republic of Ireland ( officially named Ireland ) , which covers five-sixths of the island , and Northern Ireland , which is part of the United Kingdom , in the northeast of the island . In 2011 , the population of Ireland was about 6.4 million , ranking it the second-most populous island in Europe after Great Britain . The island 's geography comprises relatively low-lying mountains surrounding a central plain , with several navigable rivers extending inland .