Brazil's Supreme Court on Tuesday voted to decriminalize the possession of marijuana for personal use, in a move that could help to reduce the country's prison population.
In future, possessing small amounts of cannabis will only be considered an administrative offence with no further legal consequences, the Supreme Court ruled.
The judges must still define the specific quantities that fall under the new rules in the coming days.
Court president Luís Roberto Barroso said: "We are not legalizing drug use or saying that it is a good thing."
Instead, he said, the judges aimed to find the most effective way to address the drug "epidemic" in Brazil, as previous strategies have failed to curb the increasing consumption and drug trafficking.
Cannabis is still an illegal substance and cannot be consumed in public, Barroso said.
The decriminalization of marijuana in Brazil could help reduce prison overcrowding. Currently, some 840,000 people are imprisoned in Brazil, many of them for possessing small amounts of drugs.
Brazil, a country of some 210 million, has the third-highest number of prisoners in the world, after the United States and China.