Dungannon (from Irish: Dún Geanainn, meaning "Geanann's stronghold") is a town in County Tyrone, Northern Ireland. It is the third-largest town in the county (after Omagh and Strabane) and had a population of 15,889 at the 2011 Census. The Dungannon and South Tyrone Borough Council has its headquarters in the town.For centuries, it was the 'capital' of the O'Neill dynasty, who dominated most of Ulster and built a castle on the hill.