a market-town of Ireland, county of Tyrone, Ulster, on the left bank of the Strule, 27 miles S. of Londonderry. It is a neat, clean, and well-built town; the houses generally of stone, and the streets lighted with gas. Among the public buildings are the county court-house, an elegant building of Grecian architecture, the county jail, district lunatic asylum, infirmary, barracks, and union workhouse. The river is crossed by a handsome stone bridge. There are a parish church, a Roman Catholic chapel, and several dissenting places of worship. Omagh was burned by James II. in 1689, and again by accident in 1743. Market-day, Saturday. Pop. (1851) 3385.