Chestnut Hill is an unincorporated community and census-designated place in Northampton County, Pennsylvania, United States. It was first listed as a CDP prior to the 2020 census. Its population as of the 2020 census was 6,689. It is part of the Lehigh Valley metropolitan area, which had a population of 861,899 and was the 68th-most populous metropolitan area in the U.S. as of 2020. Chestnut Hill is on the eastern edge of Northampton County, in the southeastern quadrant of Forks Township.