In urban planning, a historic core city or central city is the municipality with the largest 1940 population in the present metropolitan area (metropolitan statistical area). This term was retired by the US census bureau and replaced by the term principal city, which can include historic core cities and post-WWII cities. Metropolitan areas were no longer considered monocentric, but polycentric due to suburbanization of employment. A historic core city is not to be confused with the core of a metropolitan area which is defined as an urban area with a population of over 50,000 by the US census bureau.

Historic core cites in the United States often have higher detached single family housing rates, lower density, and fewer jobs than surrounding satellite cities and suburbs. A central city is usually the first settlement established in an urban region, years before the outlying districts came into existence. These cities typically contain less economic activity and more crime than their surrounding areas. Central cities often form the regional downtowns of metro areas. The term is used mainly in US context, although since the 1970s it has also become relatively common in Canada and, to a lesser extent, Europe and Australia.

The followings are the core city of the five largest metropolitan areas in the world.