The City of London, widely referred to simply as the City, is a city, ceremonial county and local government district that contains the ancient centre, and constitutes, along with Canary Wharf, the primary central business district (CBD) of London and one of the leading financial centres of the world. It constituted most of London from its settlement by the Romans in the 1st century AD to the Middle Ages, but the modern area referred to as London has since grown far beyond the City of London boundary. The City is now only a small part of the metropolis of Greater London, though it remains a notable part of central London. The City of London is not one of the London boroughs, a status reserved for the other 32 districts. It is also a separate ceremonial county, being an enclave surrounded by Greater London, and is the smallest ceremonial county in England.

City status in the United Kingdom is granted by the monarch of the United Kingdom to specific centres of population, which might or might not meet the generally accepted definition of cities. As of 22 November 2022, there are 76 cities in the United Kingdom—55 in England, seven in Wales, eight in Scotland, and six in Northern Ireland. Although it carries no special rights, the status of city can be a marker of prestige and confer local pride.