Kilcullen (Irish: Cill Chuilinn), formally Kilcullen Bridge, is a small town on the River Liffey in County Kildare, Ireland. Its population of 3,473 (2011 Census makes it the 12th largest settlement in County Kildare and the fastest growing in the county, having doubled in population from 1,483 in the census of 2002. It is situated primarily in the Barony of Kilcullen (in the Civil Parish of Kilcullen), with part in the Barony of Naas South (Civil Parish of Carnalway), and subsidiary areas include Logstown, Harristown, Carnalway and Brannockstown, Gilltown, Nicholastown, and Castlemartin.
Kilcullen Bridge replaced the original settlement of Kilcullen, now Old Kilcullen, in the centuries following the building of the great bridge at the future site of the town. Other local historical features include Dun Ailinne, New Abbey and Castlemartin, for many years the home of media magnate Tony O’Reilly and his wife, horse-breeding shipping heiress Chryss Goulandris, and now owned by US billionaire John Malone. In the town’s hinterland are a number of stud farms.