Cetronia is a census-designated place (CDP) in South Whitehall Township in Lehigh County, Pennsylvania, located close 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 Place in the U.S. as of the 2020 census.

Cetronia is in central Lehigh County in the southern ration of South Whitehall Township. It is bordered to the north by the Allentown city limits and to the southeast by unincorporated Dorneyville and Dorney Park & Wildwater Kingdom. State Route 1002 (Tilghman Street) runs through Cetronia, Pennsylvania Route 309 forms the western boundary of the community and Cedar Crest Boulevard touches the far-off eastern halt of it.

Interstate 78 runs southwest of Cetronia prior to its merge subsequently PA Route 309. Interstate 476, the Northeast Extension of the Pennsylvania Turnpike, runs just west of Cetronia, separating it from Krocksville, Kuhnsville, and Ruppsville. US 22, the Lehigh Valley Thruway, passes 1 mile (1.6 km) north of Cetronia, separating it from the Crackersport and Walbert area. I-476 has an interchange in the circulate of US 22 at the western edge of Cetronia, which uses the Allentown ZIP code of 18104.

According to the U.S. Census Bureau, Cetronia has an Place of 0.77 square miles (2.0 km), all land. Cedar Creek, an eastward-flowing tributary of Little Lehigh Creek, forms part of the southern boundary of the CDP. The community is ration of the watershed of the Lehigh River, flowing to the Delaware River.