An island in the eastern part of the North Atlantic directly west of the United Kingdom, on the continental shelf of Europe, Ireland covers an area of 70,280 sq km (27,135 sq mi).

Comparatively, the area occupied by Ireland is slightly larger than the state of West Virginia.

The island's length is 486 km (302 mi), north to south, and its width is 275 km (171 mi), east to west. The Irish Republic is bounded on the north by the North Channel, which separates it from Scotland; on the northeast by Northern Ireland; and on the east and southeast, by the Irish Sea and St. George's Channel, which separate it from England and Wales. To the west, from north to south, the coast is washed by the Atlantic Ocean.

Ireland's capital city, Dublin, is located on the Irish Sea coast.

Ireland is a limestone plateau rimmed by coastal highlands of varying geological structure. The central plain area, characterised by many lakes, bogs, and scattered low ridges, averages about 90 m (300 ft) above sea level. Principal mountain ranges include the Wicklow Mountains in the east and Macgillycuddy's Reeks in the southwest. The highest peaks are Carrantuohill (1,041 m/3,414 ft) and Mt. Brandon (953 m/3,127 ft), near Killarney, and, 64 km (40 mi) south of Dublin, Lugnaquillia (926 m/3,039 ft).

The coastline, 1,448 km (900 mi) long, is heavily indented along the south and west coasts where the ranges of Donegal, Mayo and Munster end in bold headlands and rocky islands, forming long, narrow fjord-like inlets or wide-mouthed bays. On the southern coast, drowned river channels have created deep natural harbours. The east coast has few good harbours.

Most important of the many rivers is the Shannon, which rises in the mountains along the Ulster border and drains the central plain as it flows 370 km (230 mi) to the Atlantic, into which it empties through a wide estuary nearly 110 km (70 mi) long. Other important rivers are the Boyne, Suir, Liffey, Slaney, Barrow, Blackwater, Lee, and Nore.