In urban planning, a core city, metropolitan core, or central city, is the largest or most important city of a metropolitan area. A core city is surrounded by smaller satellite cities, towns, and suburbs. A central city is usually the first settlement established in an urban region before the outlying districts came into existence, later in history. 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.[1][2][3][4]

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