Leixlip ( or ;, ) 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 2016, the population of the town was 15,504. It is the fourth largest town in Kildare, and the 29th largest in Ireland.
The placename comes from the Old Norse lax hlaup (Younger Futhark: ᛚᛅᚼᛋ ᚼᛚᛅᚢᛒ; ) which means "salmon leap". The name in the Irish language (Léim an Bhradáin) is a direct translation of this, and was first adopted in the 1890s. In Latin, it is Saltus salmonis, from which comes the names of the baronies of North Salt and South Salt.
