Kilcullen, formally Kilcullen Bridge, is a small town on the River Liffey in County Kildare, Ireland. Its population of 3,815 at the 2022 census made it the 13th largest settlement in County Kildare. From 2002 to 2011, it was one of the fastest growing towns in the county, doubling its population from 1,483 to 3,473.