Bethlehem is a city in Northampton and Lehigh Counties in the Lehigh Valley region of eastern Pennsylvania, United States. As of the 2020 census, Bethlehem had a total population of 75,781. Among its total population as of 2020, 55,639 were in Northampton County and 19,343 were in Lehigh County. It is the eighth-most populous city in the state. The city is located along the Lehigh River, a 109-mile-long tributary of the Delaware River.