United Kingdom Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe. With an area of 209,331 km2 (80,823 sq mi), it is the largest of the British Isles, the largest European island and the ninth-largest island in the world.[6][note 1] The island is dominated by a maritime climate with narrow temperature differences between seasons. The 60% smaller island of Ireland is to the west – together these islands, along with over 1,000 smaller surrounding islands and named substantial rocks, form the British Isles archipelago