Rio de Janeiro ( /ˈriːoʊ deɪ ʒəˈnɛəroʊ/ or /ˈriːoʊ deɪ dʒəˈnɛəroʊ/; Brazilian Portuguese: [ˈʁi.u dʒi ʒaˈnejɾu],River of January), commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th largest in the Americas, and 26th in the world.

The city was the capital of Brazil for nearly two centuries, from 1763 to 1815 during the Portuguese colonial era, 1815 to 1821 as the capital of the United Kingdom of Portugal, Brazil and Algarves, and 1822 to 1960 as an independent nation. Rio is nicknamed the Cidade Maravilhosa or "Marvelous City."

Rio de Janeiro represents the second largest GDP in the country (and 30th largest in the world in 2008), estimated at about R$ 343 billion (IBGE/2008) (nearly US$ 201 billion), and is the headquarters of two major Brazilian companies – Petrobras and Vale, and major oil companies and telephony in Brazil, besides the largest conglomerate of media and communications companies in Latin America, the Globo Organizations. The home of many universities and institutes, it is the second largest center of research and development in Brazil, accounting for 17% of national scientific production – according to 2005 data.

Brazil ⁱ/brəˈzɪl/ (Portuguese: Brasil, IPA: [bɾaˈziw]), officially the Federative Republic of Brazil (Portuguese: República Federativa do Brasil,  listen (help·info)), is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people. It is the only Portuguese-speaking country in the Americas and the largest lusophone country in the world.

Bounded by the Atlantic Ocean on the east, Brazil has a coastline of 7,491 km (4,655 mi). It is bordered on the north by Venezuela, Guyana, Suriname and the French overseas region of French Guiana; on the northwest by Colombia; on the west by Bolivia and Peru; on the southwest by Argentina and Paraguay and on the south by Uruguay. Numerous archipelagos form part of Brazilian territory, such as Fernando de Noronha, Rocas Atoll, Saint Peter and Paul Rocks, and Trindade and Martim Vaz. It borders all other South American countries except Ecuador and Chile.

Brazil was a colony of Portugal from the landing of Pedro Álvares Cabral in 1500 until 1815, when it was elevated to the rank of kingdom and the United Kingdom of Portugal, Brazil and the Algarves was formed. The colonial bond was in fact broken in 1808, when the capital of the Portuguese colonial empire was transferred from Lisbon to Rio de Janeiro, after Napoleon invaded Portugal.Independence was achieved in 1822 with the formation of the Empire of Brazil, a unitary state governed under a constitutional monarchy and a parliamentary system. The country became a presidential republic in 1889, when a military coup d'état proclaimed the Republic, although the bicameral legislature, now called Congress, dates back to the ratification of the first constitution in 1824. Its current Constitution, formulated in 1988, defines Brazil as a Federal Republic. The Federation is formed by the union of the Federal District, the 26 States, and the 5,564 Municipalities.