Bardonia is a hamlet and census-designated place in the town of Clarkstown, Rockland County, New York, United States. It is located northeast of Nanuet, northwest of West Nyack, south of New City, and west of Valley Cottage. The population was 4,108 at the 2010 census. Bardonia is north of the New York State Thruway. Bardonia is named for the Bardon brothers- John and the twins Phillip and Conrad- who came from Bavaria in 1849 and opened several businesses.