Slavery in Brazil began long before the first Portuguese settlement was established in 1516, with members of one tribe enslaving captured members of another. Later, colonists were heavily dependent on indigenous labor during the initial phases of settlement to maintain the subsistence economy, and natives were often captured by expeditions called bandeiras ("Flags", from the flag of Portugal they carried in a symbolic claiming of new lands for the country). The importation of African slaves began midway through the 16th century, but the enslavement of indigenous peoples continued well into the 17th and 18th centuries.

During the Atlantic slave trade era, Brazil imported more enslaved Africans than any other country in the world. An estimated 4.9 million enslaved people from Africa were imported to Brazil during the period of 1501 to 1866. Until the early 1850s, most enslaved African people who arrived on Brazilian shores were forced to embark at West Central African ports, especially in Luanda (present-day Angola).

Slave labor was the driving force behind the growth of the sugar economy in Brazil, and sugar was the primary export of the colony from 1600 to 1650. Gold and diamond deposits were discovered in Brazil in 1690, which sparked an increase in the importation of enslaved African people to power this newly profitable mining. Transportation systems were developed for the mining infrastructure, and population boomed from immigrants seeking to take part in gold and diamond mining.

Demand for enslaved Africans did not wane after the decline of the mining industry in the second half of the 18th century. Cattle ranching and foodstuff production proliferated after the population growth, both of which relied heavily on slave labor. 1.7 million slaves were imported to Brazil from Africa from 1700 to 1800, and the rise of coffee in the 1830s further expanded the Atlantic slave trade.

Brazil was the last country in the Western world to abolish the enslavement of human beings. By the time slavery was abolished, on May 13, 1888, an estimated 5.8 million enslaved people had been transported from Africa to Brazil. This was 40% of the total number of enslaved people trafficked from Africa to the Americas, according to one estimate.

The National Congress of Brazil (Portuguese: Congresso Nacional do Brasil) is the legislative body of Brazil's federal government. Unlike the state legislative assemblies and municipal chambers, the Congress is bicameral, composed of the Federal Senate (the upper house) and the Chamber of Deputies (the lower house). The Congress meets annually in Brasília from 2 February to 22 December, with a mid-term break taking place between 17 July and 1 August.The Senate represents the 26 states and the Federal District. Each state and the Federal District has a representation of three Senators, who are elected by popular ballot for a term of eight years. Every four years, renewal of either one third or two-thirds of the Senate (and of the delegations of the States and the Federal District) takes place. The Chamber of Deputies represents the people of each state, and its members are elected for a four-year term by a system of proportional representation. Seats are allotted proportionally according to each state's population, with each state eligible for a minimum of 8 seats (least populous) and a maximum of 70 seats (most populous). Unlike the Senate, the whole of the Chamber of Deputies is renewed every four years.Until recently it was common for politicians to switch parties and the proportion of congressional seats held by each party would often change. However, a decision of the Supreme Federal Court has ruled that the seats belong to the parties and not to the politicians; one can only change parties and retain his seat in a very limited set of cases. Consequently, politicians who abandon the party for which they were elected now face the loss of their congressional seat. Each house of the Brazilian Congress elects its president and the other members of its directing board from among its members. The President of the Senate is ex officio the President of the National Congress, and in that capacity summons and presides over joint sessions, as well as over the joint services of both houses. The President of the Chamber is second in the presidential line of succession while the President of the Senate (and of Congress) is third.