a market-town of Ireland, in the county of Armagh, on the Upper Bann river, which is here crossed by a fine bridge 10 miles N.E. of Armagh, and 84 N. by W. of Dublin. It is well built and paved, containing a parish church in the early English style; also Presbyterian, Methodist, and Roman Catholic places of worship, endowed and national schools, a good market-house, a dispensary, and a loan society, which has done much for the encouragement of industry in the neighbourhood. The manufacture of linen, lawn, cumbrie, &c., gives employment to many of the inhabitants; and the town contains besides, large corn-mills, a manufactory of steam-engines and other machinery, and a soap and candle work. Markets for the sale of cattle, pork, and rural produce are held at Portadown on Saturdays; and there are also monthly and annual fairs. Pop. (1851) 3091.