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%.[7][8] There are twenty-six extant mammal species native to Ireland. A Norman invasion in the Middle Ages gave way to a Gaelic resurgence in the 13th century.

Over sixty years of intermittent warfare in the 1500s led to English dominance after 1603. 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 Ireland which remained a part of the United Kingdom.

Northern Ireland saw much civil unrest from the late 1960s until the 1990s. This subsided following a political agreement in 1998. In 1973, both parts of Ireland joined the European Economic Community.