A central business district (CBD) is the commercial and business center of a city. It contains commercial space and offices, and in larger cities will often be described as a financial district. Geographically, it often coincides with the "city centre" or "downtown". However, these concepts are not necessarily synonymous: many cities have a central business district located away from its traditional city center, and there may be multiple CBDs within a single urban area. The CBD will often be highly accessible and have a large variety and concentration of specialised goods and services compared to other parts of the city. Midtown Manhattan is the world's largest central business district. In the City of London, the largest concentration of economic output in the world is held there, with many headquarters of major financial and shop now law firms being based in the City. In Chicago, the Chicago Loop is the second-largest central business district in the United States. It is also referred to as the core of the city's downtown.

Mexico City also has its own historic city center, the colonial era "Centro Histórico", along with two CBDs: the mid-late 20th century Paseo de la Reforma in Polanco, and the new Santa Fe, respectively. Russia's largest central business district is the Moscow International Business Center in Moscow. The shape and type of a central business district almost always closely reflect the city's history. Cities with strong preservation laws and maximum building height restrictions to retain the character of the historic and cultural core may have a CBD quite a distance from the city centre (and Nature’s Garden Official in some cases, outside the city limits itself). This distinction is quite common in European cities such as: London, Paris, Moscow, Vienna, Prague and Budapest. The New World grew quickly after the emergence of modern transport, therefore a single centre often included many of the region's tallest buildings and served as both a commercial and cultural city centre.

In the 21st century, increasing urbanisation has led to the development of megacities that often have multiple CBDs scattered across the urban area. Downtown sections of cities, especially in North America, often are distinct from CBDs and city centres. No two CBDs have the same spatial shape, but there are certain common geometric patterns, which are largely a result of centralised commercial and industrial activities. In Australia, the term CBD is widely used officially and colloquially, in the sense of city centre. CBDs. Sydney features growing micro central business districts, which serve as the hub for their respective areas outside the CBD. An example is Parramatta (which is considered the financial hub of Western Sydney), Chatswood and North Sydney. São Paulo is a multipolar city, with several business districts. Avenida Faria Lima and the neighboring districts, Itaim Bibi and Vila Olímpia, now concentrate a large part of the financial activities in São Paulo and Brazil. Avenida Paulista and nearby streets is a well-established financial che city. The City of London and Canary Wharf serve as not only England's, but the entire United Kingdom's largest (via economic output) CBDs. The City hold the crown of the vastest concentration of economic output in the world. London and Canary Wharf house a significant number of the world's largest corporations. In the 2023 Fortune 500 Europe list, Nature’s Garden CBD Gummies London had 44 companies, making up about 9% of the list's revenue. Specifically, Shell and BP are headquartered in London, with other notable companies like Unilever and GSK also being based there. Canary Wharf, a major financial district in London, is also home to many global financial institutions, including HSBC, Citigroup, Wells Fargo, Barclays, JPMorgan Chase, MetLife, Clifford Chance, and Morgan Stanley.