Portadown () is a town in County Armagh, Northern Ireland. The town sits on the River Bann in the north of the county, about southwest of Belfast. It is in the Armagh City, Banbridge and Craigavon Borough Council area and had a population of about 22,000 at the 2011 Census. For some purposes, Portadown is treated as part of the "Craigavon Urban Area", alongside Craigavon and Lurgan.
Although Portadown can trace its origins to the early 17th century Plantation of Ulster, it was not until the Victorian era and the arrival of the railway that it became a major town. It earned the nickname "hub of the North" due to it being a major railway junction; where the Great Northern Railway's line diverged for Belfast, Dublin, Armagh and Derry. In the 19th and 20th centuries Portadown was also a major centre for the production of textiles (mainly linen).
Portadown is the site of the long-running Drumcree dispute, over yearly marches by the Protestant Orange Order through the Catholic part of the town, which often sparked violence and protests. In the 1990s, the dispute escalated and prompted a massive security operation, drawing worldwide attention to Portadown.
The Portadown area had long been populated by Irish Gaels. At the beginning of the 1600s, it lay within the district of Clancann (Clann Chana), which was part of the larger territory of Oneilland (Uí Nialláin). This district was named after the dominant local clan—the McCanns (Mac Cana)—who had been in the area since before the 13th century. The McCanns were then a vassal sept of the O'Neills (Uí Néill). On the eastern banks of the River Bann was the district of Clanbrasil (Clann Bhreasail).
The town's name comes from the Irish Port a' Dúnáin (or, more formally, Port an Dúnáin), meaning the port or landing place of the small fort. This was likely a fort of the McCanns.
From 1594 until 1603, the O'Neills and an alliance of other clans fought in the Nine Years' War against the Tudor conquest of Ireland. This ended in defeat for the Irish clans, and much of their land was seized and redistributed by the Crown.