Cetronia is a census-designated place in South Whitehall Township in Lehigh County, Pennsylvania, located near Allentown. As of the 2020 census, its population was 2,421. Cetronia 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 the 2020 census.