Claim: Ireland was the second-most populous island in Europe in May 2011.

Great Britain , also known as Britain , is a large island in the north Atlantic Ocean off the northwest coast of continental Europe . With an area of 209,331 km2 , Great Britain is the largest of the British Isles , the largest European island , and the ninth-largest island in the world . In 2011 the island had a population of about 61 million people , making it the world 's third-most populous island after Java in Indonesia and Honshu in Japan . The island of Ireland is situated to the west of it , and together these islands , along with over 1,000 smaller surrounding islands , comprise the British Isles archipelago .   The island is dominated by a maritime climate with quite narrow temperature differences between seasons . Politically , the island is part of the United Kingdom of Great Britain and Northern Ireland , and constitutes most of its territory . Most of England , Scotland , and Wales are on the island . The term `` Great Britain '' often extends to include surrounding islands that form part of England , Scotland , and Wales , and is also sometimes loosely applied to the UK as a whole .   A single Kingdom of Great Britain resulted from the union of the Kingdom of England -LRB- which had already comprised the present-day countries of England and Wales -RRB- and the Kingdom of Scotland by the 1707 Acts of Union . More than a hundred years before , in 1603 , King James VI , King of Scots , had inherited the throne of England , but it was not until 1707 that the two countries ' parliaments agreed to form a political union . In 1801 , Great Britain united with the neighbouring Kingdom of Ireland , forming the United Kingdom of Great Britain and Ireland , which was renamed the `` United Kingdom of Great Britain and Northern Ireland '' after the Irish Free State seceded in 1922 .