Brasília (Portuguese pronunciation: [bɾaˈziliɐ]) is the capital of Brazil. The name is commonly spelled Brasilia in English. The city and its District are located in the Central-West region of the country, along a plateau known as Planalto Central. It has a population of about 2,557,000 (3,599,000 in the metropolitan area) as of the 2008 IBGE estimate, making it the fourth largest city in Brazil, ahead of Belo Horizonte and Fortaleza — see also List of urban agglomerations by population (United Nations). However, as a metropolitan area, it ranks lower at sixth. It is listed as a World Heritage Site by UNESCO. Brasília hosts 91 foreign embassies.

As the national capital, Brasília is the seat of all three branches of the Brazilian government. The city also hosts the headquarters of many Brazilian companies such as the Banco do Brasil, Caixa Econômica Federal, Correios and Brasil Telecom. The city is a world reference for urban planning. The locating of residential buildings around expansive urban areas, of building the city around large avenues and dividing it into sectors, has sparked a debate and reflection on life in big cities in the 20th century. The city's planned design included specific areas for almost everything, including accommodation, Hotel Sectors North and South. However, new areas are now being developed as locations for hotels, such as the Hotels and Tourism Sector North, located on the shores of Lake Paranoá.

The city was planned and developed in 1956 with Lúcio Costa as the principal urban planner and Oscar Niemeyer as the principal architect. In 1960, it formally became Brazil's national capital. When seen from above, the main planned part of the city's shape resembles an airplane or a butterfly. The city is commonly referred to as Capital Federal, or simply BSB. People from the city of Brasília are known as brasilienses or candangos.

Brasília has a sui generis status in Brazil, given that it is not a municipality like nearly all cities in Brazil. Although there is no legal definition for Brasília, the term is almost always used synonymously with the Brazilian Federal District, and thus constitutes an indivisible Federative Unit, analogous to a state. In the region, however, the word Brasília often refers only to the First Administrative Region within the Distrito Federal (Federal District), also known as "Plano Piloto," where the most important government buildings are located. This is in contrast with the surrounding "satellite cities," which nevertheless are also part of the Federal District, and as such, Brasília, in a broader sense.

Brasília International Airport is a major airline hub for the rest of the country, connecting the capital to all major Brazilian cities and many international destinations. It is the third most important airport of Brazil, in terms of passengers and aircraft movements.