Leixlip is a town in north-east County Kildare, Ireland. Its location on the confluence of the River Liffey and the Rye Water has marked it as a frontier town historically: on the border between the ancient kingdoms of Leinster and Brega, as an outpost of The Pale, and on Kildare's border with County Dublin. Leixlip was also a civil parish in the ancient barony of Salt North. As of 2022, the population of the town was 16,773.