Leixlip is located at the confluence of the two rivers the Liffey and the Rye. These two rivers brought with them human habitation and development there is evidence of stone-age remains in Leixlip which are some 5500 years old.

The Leixlip spa was discovered in 1793 by workmen carrying out works on behalf of the Royal Canal. Leixlip thermal spa is the only thermal spa in Ireland.

In 1948 the ESB completed the Hydro-electric dam in Leixlip.

The Leixlip Water Treatment Plant is the second largest water treatment plant in Ireland and supplies drinking water to the Greater Dublin Region including Fingal, South Dublin, Dublin City and areas of Kildare and Meath. The plant requires further expansion to cater for the rapidly growing water demands of the region