The Lerr River is a tributary within the Barrow Catchment in County Kildare, Ireland, flowing through agricultural lowland terrain in the southeastern part of the country. A relatively modest river in scale, the Lerr supports a healthy mixed fishery with both brown trout and Atlantic salmon present, making it a rewarding destination for anglers seeking a quieter, less pressured experience than the main River Barrow. The river's character is defined by riffle-dominated habitat with gravel and cobble substrate, clear water, and riparian vegetation that includes mosses, liverworts, and aquatic plants such as Ranunculus sp. — classic indicators of a clean, well-oxygenated stream environment well-suited to salmonid production.