The sentence came swiftly after a conviction ruling by a panel of five justices on Brazil's Supreme Court, making the 70-year-old Bolsonaro the first former president in the country's history to be convicted for attacking democracy.
"This criminal case is almost a meeting between Brazil and its past, its present and its future," Justice Carmen Lucia said before her vote to convict Bolsonaro, referring to a history checkered with military coups and attempts to overthrow democracy.
There was ample evidence that Bolsonaro, who is currently under house arrest, acted "with the purpose of eroding democracy and institutions," she added.
Four of the five judges voted to convict the former president of five crimes: taking part in an armed criminal organisation; attempting to violently abolish democracy; organising a coup; and damaging government property and protected cultural assets.
The conviction of Bolsonaro, may further enrage his close ally US President Donald Trump, who had called the case a "witch hunt" and in retaliation hit Brazil with tariff hikes, sanctions against the presiding judge, and the revocation of visas for most of the high court justices.
Asked about the conviction on Thursday, Trump again praised Bolsonaro, calling the verdict "a terrible thing."
"I think it's very bad for Brazil," he added.
As he watched his father's conviction from the US, Brazilian Congressman Eduardo Bolsonaro told Reuters he expected Trump to consider imposing further sanctions on Brazil and its high court justices.
US Secretary of State Marco Rubio said on X the court had "unjustly ruled," adding: "The United States will respond accordingly to this witch hunt."
Brazil's Foreign Ministry issued a statement calling Rubio's comment a threat that "attacks Brazilian authority and ignores the facts and the compelling evidence in the records." The ministry said that Brazilian democracy would not be intimidated by the US
President Luiz Inacio Lula da Silva also said he does not fear new sanctions from the US in an interview to local TV channel Band hours before Bolsonaro's conviction was confirmed.
The verdict was not unanimous, with Justice Luiz Fux on Wednesday breaking with his peers by acquitting the former president of all charges and questioning the court's jurisdiction.
Bolsonaro's lawyers said in a statement that the sentencing "was absurdly excessive" and that it would file the appropriate appeals.
Anti-establishment anger opened the path for Bolsonaro's successful 2018 presidential run, with dozens of far-right and conservative lawmakers elected on his coattails. They have reshaped Congress into an enduring obstacle to Lula's progressive agenda.
As he faced a tough reelection campaign against Lula in 2022 - which Lula went on to win - Bolsonaro's comments took on an increasingly messianic quality, raising concerns about his willingness to accept the results.
In 2023, Brazil's electoral court barred him from public office until 2030 for venting unfounded claims about Brazil's electronic voting system.
The cases have largely been led by the commanding figure of Justice Alexandre de Moraes, appointed to the court by a conservative president in 2017, whose hardball approach to Bolsonaro and his allies has been celebrated by the left and denounced by the right as political persecution.
The verdict marks the first time since Brazil became a republic almost 140 years ago that military officials have been punished for attempting to overthrow democracy.
