City networks are the connections between cities. These networks can be of different nature and of different importance. In modern conceptions of cities, these networks play an important role in understanding the nature of cities. City networks can be physical connections to other places, such as railways, canals or scheduled flights. City network also exist in immaterial form, such as trade, global finance, markets, migration, cultural links, shared social spaces or shared histories. There are also networks of religious nature, in particular through pilgrimage.

The city itself is then regarded as the node where different networks run together. Some of these networks are more powerful than others, for networks of global finance are currently dominant. Some urban thinkers have indeed argued that cities can only be understood if the context of the city's connections is understood.

Neither the connections through city networks nor the dominance of particular networks are dominant or fixed. Religious networks were of greater importance in Europe in the past, whilst today arguably economic ones predominate. The case of Moscow illustrates well how city networks are not fixed. During the time of the Soviet Union, Moscow was the most powerful city because of its powerful political networks. With the end of the Cold War, however, the importance of this political network quickly changed and in Moscow now economic networks dominate. The essence of modern city conceptions, however, is that all these networks are seen as co-existent. This overlapping of different networks allows to explain why cities are so different.

It has been argued that city networks are a key ingredient of what defines a city, alongside with the sheer number of people (density) and the particular way of life in cities.