Sunday's protests, organised by social movements, unions and political parties, denounced politicians trying to avoid legal consequences for themselves and Bolsonaro, who was sentenced to prison for a coup plot after his supporters stormed government buildings following his 2022 election defeat.
It was the first major demonstration since Bolsonaro's conviction this month, with numbers rivalling recent right-wing protests against his sentencing in major cities, driving home the stark divisions in one of the world's largest democracies.
"I hope today's demonstration outnumbers the one held by the right wing, so we can put pressure on Congress," said Renato Fonseca, a 63-year-old advertising professional in Sao Paulo with a T-shirt reading "1964 Never Again" - a reference to the coup that triggered a brutal two-decade military dictatorship in Brazil that ended in 1985.
"We came very close to a coup by Bolsonaro. I was young in 1964, but I never imagined we would be so close to another dictatorship," he said.
The Supreme Court's conviction of Bolsonaro and his co-conspirators in the government and armed forces marked the first time Brazil has punished military officers for attempting to overthrow democracy in a history stained by violent coups.
Bolsonaro is under house arrest until he exhausts appeals of his 27-year prison sentence, but allies are already working to support him via political channels, ranging from legislative amnesty to a pardon from the next president.
A conservative majority in the lower house of Congress voted last week to fast-track a bill that could grant relief for former Bolsonaro and his supporters imprisoned for taking part in the 2023 storming of government buildings.
Politicians in the lower house also seized the moment to pass a proposed constitutional amendment last week giving Congress the power to block criminal prosecution of federal MPs.
"Today's demonstrations show that the population does not want impunity or amnesty. The national Congress must focus on measures that benefit the Brazilian people," President Luiz Inacio Lula da Silva said in a social media post, sharing pictures from the protests.
Some 40,000 demonstrators filled several blocks of Sao Paulo's Avenida Paulista according to crowd estimates from researchers at the University of Sao Paulo, to protest those efforts in Congress and celebrate Bolsonaro's sentencing.
It was the strongest turnout for protests organised by Brazil's left since at least October 2022, when throngs filled the same avenue to celebrate the election of President Lula.
Organisers unfurled a nearly 15m Brazilian flag with the words "No Amnesty," in contrast with a similarly sized pro-Bolsonaro protest a couple weeks earlier, where demonstrators rolled out a huge US flag to celebrate President Donald Trump's efforts to intervene and pressure Brazilian judges and the country's judiciary on Bolsonaro's behalf.
"Brazil belongs to Brazilians. I came to defend democracy, stand against extremism, and say no to immunity and amnesty for coup plotters," said Scarlett Angelotti, a 62-year-old educator in Sao Paulo wearing the soccer jersey of Brazil's national team.
with DPA
