Guanabara Bay is an oceanic bay located in Southeast Brazil in the state of Rio de Janeiro. On its western shore lie the cities of Rio de Janeiro and Duque de Caxias, and on its eastern shore the cities of Niterói and São Gonçalo. Four other municipalities surround the bay's shores. Guanabara Bay is the second largest bay in area in Brazil, at 412 square kilometres (159 sq mi), with a perimeter of 143 kilometres (89 mi).

The Southeast Region of Brazil is composed of the states of Espírito Santo, Minas Gerais, Rio de Janeiro and São Paulo. It is the richest region of the country, responsible for approximately 60% of the Brazilian GDP, as São Paulo, Rio de Janeiro, and Minas Gerais are the three richest states of Brazil, the top three Brazilian states in terms of GDP. The Southeast of Brazil also has the highest GDP per capita among all Brazilian regions.