Ireland is an island to the north-west of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth. To its east is the island of Great Britain, from which it is separated by the Irish Sea.
Politically, Ireland is divided between the Republic of Ireland, which covers five-sixths of the island, and Northern Ireland, a part of the United Kingdom, which covers the remaining area and is located in the north-east of the island. The population of Ireland is approximately 6.4 million. Just under 4.6 million live in the Republic of Ireland and just over 1.8 million live in Northern Ireland.
The island's geography comprises relatively low-lying mountains surrounding a central plain, with several navigable rivers extending inland. The island has lush vegetation, a product of its mild but changeable oceanic climate, which avoids extremes in temperature. Thick woodlands covered the island until medieval times. Today, the amount of land that is forested in Ireland is just one third of the European average of 35%. There are twenty-six extant mammal species native to Ireland.
Gaelic Ireland emerged some time in prehistory and lasted until the early 17th century. The island was converted to Christianity from the 5th century onward. Following the Norman invasion in the 12th century, England claimed sovereignty over Ireland. However, English rule did not extend over the whole island until the 16th–17th century Tudor conquest. This led to the colonization of northern Ireland by settlers from Britain. In the 1690s, a system of Protestant English rule was designed to materially disadvantage the Catholic majority and Protestant dissenters, and was extended during the 18th century. In 1801, Ireland became a part of the United Kingdom. A war of independence in the early 20th century was followed by the partition of the island, creating the Irish Free State, which became increasingly sovereign over the following decades, and Northern...