Longford, county in the province of Leinster, north-central Ireland. The town of Longford, in the west-central part of the county, is the county seat.
County Longford is bounded by Counties Leitrim (northwest), Cavan (northeast), Westmeath (southeast), and Roscommon (west). The main features of drainage are the valleys of the Rivers Shannon, Erne, and Inny and Loughs (Lakes) Gowna and Ree. The surface of the county, generally a part of lowland Ireland, rises from the Shannon to elevations of 200 to 400 feet (60 to 120 metres), but there are isolated hills and ranges. The lowland is thickly plastered with glacial drifts and has large areas of bog.
Most farms occupy less than 30 acres (12 hectares), and their main concern is the raising of cattle, chiefly for export to the richer and larger farms of Meath. Major crops include oats and potatoes. There is also some dairying. About one-fourth of the county’s population lives in towns, of which the largest is Longford.
Longford, whose early name was Annaly, or Anale, was a principality of the O’Farrells and was originally part of County Meath. In the 12th century it was granted by Henry II to Hugh de Lacy, who started an English colony there. On the division of Meath into two counties in 1543, Annaly was included in Westmeath. By 1569 it was a shire under the name of Longford. Area 421 square miles (1,091 square km). Pop. (2002) 31,068; (2011) 39,000.