A primate city^[1] is a city that is the largest in its country, province, state, or region, and disproportionately larger than any others in the urban hierarchy.^[2] A primate city distribution is a rank-size distribution that has one very large city with many much smaller cities and towns and no intermediate-sized urban centers, creating a statistical king effect.^[3]

The law of the primate city was first proposed by the geographer Mark Jefferson in 1939.^[4] He defines a primate city as being "at least twice as large as the next largest city and more than twice as significant."^[5] Aside from size and population, a primate city will usually have precedence in all other aspects of its country's society such as economics, politics, culture, and education. Primate cities also serve as targets for the majority of a country or region's internal migration.

In geography, the phenomenon of excessive concentration of population and development of the main city of a country or a region (often to the detriment of other areas) is called urban primacy or urban macrocephaly.^[6]

Urban primacy can be measured as the share of a country's population that lives in the primate city.^[7] Relative primacy indicates the ratio of the primate city's population to that of the second largest in a country or region.^[8]

There is debate as to whether a primate city serves a parasitic or generative function.^[9] The presence of a primate city in a country may indicate an imbalance in development—usually a progressive core and a lagging periphery—on which the city depends for labor and other resources.^[10] However, the urban structure is not directly dependent on a country's level of economic development.^[2]

Many primate cities gain an increasing share of their country's population. This can be due to a reduction in blue-collar population in the hinterlands because of mechanization and automation. Simultaneously, the number of educated employees in white-collar endeavors such as politics, finance, media, and higher education rises. These sectors are clustered predominantly in primate cities where power and wealth are concentrated.^{[citation needed]}

Some global cities are considered national or regional primate cities.^[5][11] An example of a global city that is also a primate city is Istanbul in Turkey. Istanbul serves as the primate city of Turkey due to the unmatched economic, political, cultural, and educational influence that the city possesses in comparison to other Turkish cities such as the capital Ankara, İzmir, or Bursa. Mexico City, Paris, Cairo, Jakarta, and Seoul have also been described as primate cities of their respective countries.^[12] However, not all regions and countries possess a primate city. The United States has never had a primate city on a national level due to the decentralized nature of the country and because the country's second-largest city, Los Angeles, is not far behind the country's largest city, New York City, in either population or GDP. The metropolitan area of New York City has over 19 million residents, while that of Los Angeles has roughly 13 million residents, as of 2022.^[13]

Sub-national divisions can also have primate cities. For instance, New York City is New York State's primate city, because its population is 32 times bigger than the state's second-largest city of Buffalo. New York City has 44% of the population and 65% of the GDP of New York State.^[14] The city of Anchorage is another U.S. example, with around 40% of the total population of Alaska living within the city's limits. China does not have a primate city at a national level, but several provincial capitals are disproportionately larger than other urban areas in the respective provinces. For example, Henan, Hubei, and Sichuan have provincial capitals (Zhengzhou, Wuhan, and Chengdu, respectively) that are significantly larger than the second-largest cities in those provinces, and each of those provinces has a population similar to that of a large European country.^{[citation needed]} India does not have a primate city, as Delhi is not much larger than Mumbai or Kolkata in terms of population. However, many Indian states, such as Karnataka, West Bengal, Tamil Nadu and Maharashtra, do have primate cities: Bangalore, Kolkata, Chennai, and Mumbai, respectively. Other Indian states, such as Uttar Pradesh and Kerala, do not have any primate cities.^[15]

Bangkok, the capital of Thailand, has been called "the most primate city on Earth": in 2000 it was 40 times larger than the second-largest city of that time, Nakhon Ratchasima.^[16] As of 2022, Bangkok is nearly nine times larger than Thailand's current second-largest city of Chiang Mai, which has been growing in population and has also had its boundaries expanded to reflect that growth.^[17][18] Taking the concept from his examination of the primate city during the 2010 Thai political protests and applying it to the role that primate cities play if they are national capitals, researcher Jack Fong noted that when primate cities like Bangkok function as national capitals, they are inherently vulnerable to insurrection by the military and the dispossessed. He cites the fact that most primate cities serving as national capitals contain major headquarters for the country. Thus, logistically, it is rather "efficient" to target a national capital that is also a primate city; most of the governing power is contained in that one small area, and so are most of the people.^[19]

The metropolitan area of the city of Moscow, the capital of Russia, is almost four times the size of the metropolitan area of the next largest city, Saint Petersburg,^[20][21] and plays a unique and uncontested role of the cultural and political center of the country.^[22] It can therefore be considered a primate city.

Primate cities need not be capital cities: governments may establish a new capital city in an attempt to challenge the primacy of the largest city or provide more balanced growth. For example, in Tanzania, Dar es Salaam is still the primate city even though the capital was moved to Dodoma, a new city built to a plan, in 1996. A similar process (though without building a planned city) occurred when the existing city of Wellington was chosen as New Zealand's capital in 1865; Auckland had been the capital, and commanded a greater share of the population and economy.

• Capital city
• Primate (disambiguation)
• Global city
• Megacity
• Metropolis
• Rank–size distribution
• Secondary city