The number of indigenous people within Brazil fell from 6 million in the 1500s to 100,000 in the 1950s.
The roughly 2000 nations of mostly semi-nomadic native tribes of pre-Columbian era Brazil steadily disappeared after the arrival of European settlers. Millions died from disease, war, and slavery over the centuries. Many others were assimilated into the Brazilian population. Today, the Brazilian indigenous population is on a slow rebound after an all-time low population of around 100,000 in the 1950s. There are now around 735,000 indigenous people living in 24 of the 27 states in Brazil. Among them there are 235 different ethnicities speaking over 170 unique languages.
You can learn more about the indigenous people of Brazil at the Society for Threatened People's website.