town, seat, and district (established 1973), formerly in County Antrim, Northern Ireland. Antrim town is located in the valley of the Six Mile Water stream, at the northeastern corner of Lough (lake) Neagh. In 1798, the town was the scene of a battle in which several thousand nationalist (essentially Presbyterian) insurgents, led by the United Irishmen rebel Henry Joy McCracken, were defeated by the British military. Just north is one of the finest examples of the Irish round (watch) towers, dating from the 10th century; it is 93 feet (28 metres) high and 17 feet (5 metres) in diameter. Antrim Castle, built in the 17th century, is evidence of the town's earlier strategic importance. A busy market centre and road junction, Antrim town was formerly an important locale for the linen industry.

Antrim district's topography consists of high, rolling moorlands gradually descending to the Bann Valley and the lowlands along the shoreline of Lough Neagh, the largest inland lake in the United Kingdom. Antrim borders the districts of Ballymena to the north, Newtownabbey to the east, and Belfast and Lisburn to the south and encompasses the villages of Crumlin, Randalstown, Toomebridge, Templepatrick, and Parkgate in addition to the town of Antrim. It supports considerable farming activity, mostly in livestock. Important synthetic-fibre companies were established in the district in the 1970s, and service industries are scattered throughout. Antrim district is traversed by a national highway that extends from Belfast to Randalstown. Belfast's international airport is located at Aldergrove, 7 miles (11 km) south of Antrim town. Area district, 221 square miles (572 square km). Pop. (2001) town, 20,001; (2004 est.) district, 49,833.

Antrim was bounded by the Atlantic Ocean (north), the North Channel and the Irish Sea (east), Belfast Lough (inlet of the sea) and the River Lagan (south), and by Lough (lake) Neagh (Neagh, Lough) and the lower River Bann (west).

Its northern and eastern parts were composed of the Antrim Mountains, an ancient basalt plateau of moorland and peat bogs cut by deep glens, ending at its northeastern corner in Fair Head (635 feet 【194 m】), a perpendicular cliff. Collapse of the basalt caused the depression holding Lough Neagh, the largest inland lake in the British Isles. Prominent peaks in Antrim included Trostan (1,817 feet), Knocklayd (1,695 feet), and Slieveanorra (1,676 feet); Divis (1,574 feet) is the highest of the Belfast hills. The basalt reaches the north coast as steep cliffs and, at the Giant's Causeway, forms perpendicular hexagonal columns.

Man probably first came to Ireland through Antrim from western Scotland. Quantities of flint implements, or tools, dating from about 6000 BC occur in the Lough Neagh district. Migrations between Ireland and Scotland were common, especially in the 6th century AD. Scandinavian invaders reached Lough Neagh but made no permanent settlements. Antrim was partially penetrated by Anglo-Norman adventurers during the 12th century and formed part of the earldom of Ulster. Disorders in the late Middle Ages and the invasion by Edward Bruce (later king of Ireland) and his army from Scotland in 1315 caused the decline of English power. Only Carrickfergus remained in English hands until the Tudor period (1485–1603), when attempts were made to colonize the county and many Scots settled there. Although Antrim was not part of the territory involved in the scheme for the plantation of Ulster, it continued to attract many English immigrants.

At one time Carrickfergus was the county town (seat); but, when Belfast became the site of a new county courthouse in 1847, the grand jury also moved there. In 1898, however, Belfast became a county borough, and for a time the county lacked a county town. Until 1973 Ballymena filled that role. In the 1973 administrative reorganization of Northern Ireland, the county was divided into the districts of Moyle, Ballymoney, Ballymena, Larne, Antrim, Carrickfergus, Newtownabbey, and Belfast, and portions of Coleraine, Lisburn, Castlereagh, and Craigavon districts.