Casterton is a small village and civil parish close to Kirkby Lonsdale on the River Lune in the south east corner of Cumbria, England. In the 2001 census the parish had a population of 500, decreasing at the 2011 census to 425.
The parish is bounded by Kirkby Lonsdale, Barbon, Dent, Leck and Burrow-with-Burrow, and lies just inside the western edge of the Yorkshire Dales National Park: much of the Three Counties System, the longest explored natural cave system in the country, lies beneath it. The western boundary, towards Kirkby Lonsdale, is formed by the river and has one of the finest medieval bridges in the country, one of those known as Devil's Bridge and a local landmark.
