Isle of Man, island, United Kingdom, in the Irish Sea, about midway between the coasts of Northern Ireland and England. It includes the Calf of Man, a rocky islet off the southwestern coast. The shore of the Isle of Man is lined with tall cliffs and indented by bays. Most of the surface is covered with wooded glens and rounded hills that reach their greatest height in Snaefell (621 m/2,037 ft above sea level). A mild climate makes possible the growth of many subtropical plants. More than half of the island area is devoted to agriculture; flowers, fruits, vegetables, and grains are produced. Other occupations are the raising of livestock; dairying; fishing; and the mining or quarrying of small quantities of lead, zinc, nickel, iron, copper, slate, granite, sandstone, and limestone. Native to the island is the Manx cat, characterized by the absence of a tail. The Isle of Man is a popular tourist resort.

During the early Celtic Christian era, the Isle of Man was closely associated with Ireland. It fell under Norwegian control in the 9th century and was ruled by Norway until the 13th century, when it was ceded to Scotland. During the following century it was alternately ruled by Scotland and England, finally being granted to the latter in 1346. Among the important historical remains on the island are prehistoric stone pile dwellings, runic and druidic monuments, and ancient forts, castles, round towers, and stone crossings.

The island is governed by the Court of Tynwald, consisting of an 11-member legislative council, or upper house, at the head of which is a crown-appointed lieutenant governor; and by the House of Keys, or lower house, composed of 24 elected representatives.

Manx, a language of the Goidelic group of Celtic tongues, persists among a small segment of the population, but English is the principal language of the island.

Principal seaport towns include Douglas (the capital), Ramsey, Peel, and Castletown. Area of the island, 572 sq km (221 sq mi); population (2007 estimate) 75,831.