For a list of the largest cities of the European Union by population, see List of cities in the European Union by population within city limits. The study of urban areas is useful to analyse how cities develop, which in turn can be used to define transportation, planning and environmental policies, to adjust administrative boundaries etc.

The United Nations uses three definitions for what constitutes a city, as not all cities in all jurisdictions are classified using the same criteria. Cities may be defined as the cities proper, the extent of their urban area, or their metropolitan regions.The largest city by population using the city proper definition, which is the area under the administrative boundaries of a local …