The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom or Britain Ëbrɪ.tÉn , is a sovereign state located off the northwestern coast of continental Europe. The country includes the island of Great Britain , the northeastern part of the island of Ireland, and many smaller islands. Northern Ireland is the only part of the UK that shares a land border with another state: the Republic of Ireland. Apart from this land border, the UK is surrounded by the Atlantic Ocean, with the North Sea in the east and the English Channel in the south; the Irish Sea separates Great Britain from Ireland. The UK has an area of 243,610 square kilometres , making it the 78th largest sovereign state in the world and the 11th largest in Europe.