Leonia is a borough in Bergen County, in the U.S. state of New Jersey. As of the 2020 United States census, the borough's population was 9,304, an increase of 367 from the 2010 census count of 8,937, which in turn reflected an increase of 23 from the 8,914 counted in the 2000 census. The borough is a suburb of New York City, near the western approach to the George Washington Bridge.