Brasília (bɾaˈziʎɐ) is the federal capital of Brazil and the seat of government of the Federal District. Administratively, the city is located in the Federal District which is in the Central-West Region. Physically, it is located in the Brazilian Highlands. It has a population of about 2,562,963 (3,716,996 in the metropolitan area) as of the 2008 IBGE estimate, making it the fourth largest city in Brazil. However, as a metropolitan area, it ranks lower at sixth in population. Brasília is the largest city in the world that did not exist at the beginning of the 20th century.

Brasília has the fifth largest GDP among Latin American cities and the third in Brazil. At around R$62,000 Brazilian reais (equal to approximately $30,900 US dollars or €23,000 euros), the city's per capita income is the highest among Brazil's largest cities.

As the national capital, Brasília is the seat of all three branches of the federal government of Brazil. The city also hosts the headquarters of many Brazilian companies. Planning policies such as the location of residential buildings around expansive urban areas, as well as building the city around large avenues and dividing it into sectors, have sparked a debate and reflection on life in big cities in the 20th century. The city's design divides it into numbered blocks as well as sectors for specified activities, such as the Hotel Sector, the Banking Sector or the Embassy Sector. Brasília hosts 124 foreign embassies.

The city was planned and developed in 1956 with Lúcio Costa as the principal urban planner, Oscar Niemeyer as the principal architect and Roberto Burle Marx as the landscape designer. Brasília is in the Unesco's World Hertitage List due to its architecture. On April 22, 1960, it formally became Brazil's national capital. Viewed from above, the main portion of the city resembles an airplane or a butterfly. The city is commonly referred to as Capital Federal, or simply BSB. Residents of Brasília are known as brasilienses or candangos (the latter referring to those not born in the city but who migrated there after it was established).

In local usage, the word "Brasília" usually refers only to the First Administrative Region (RA I) within the Federal District (Distrito Federal), where the most important government buildings are located. Brasília has a unique status in Brazil, as it is an administrative division rather than a legal municipality like nearly all cities in Brazil. Nationally, the term is almost always used synonymously with the Federal District, which constitutes an indivisible Federative Unit, analogous to a state. Several "satellite cities" exist which are also part of the Federal District.

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