Chad's former president Hissene Habre was found guilty and sentenced to life in prison for crimes against humanity, war crimes, torture and sexual slavery by a Senegalese court on Monday.
The case against 73-year-old Habre was the first-ever trial of a former head of state in sub-Saharan Africa.
"Impunity and terror were the law" during Habre's eight-year rule from 1982 to 1990, said judge Gberdao Gustave Kam, highlighting the "extreme gravity of the crimes."
Millions of people had fallen victim to Habre's regime, "many of whom still suffer the consequences, almost 30 years later," said Kam.
Habre was found guilty of having coordinated crimes against humanity, which included illegal detention, repression and sexual slavery. The judges concluded that Habre had systematically hunted down opponents, personally committed rape and torture and given orders for execution in writing.
Habre, who has been nicknamed "Africa's Pinochet" after Chilean military dictator Augusto Pinochet, was given two weeks to appeal the verdict.
Wearing a white turban that covered his head and mouth and hiding his eyes behind gold-rimmed sunglasses, Habre sat immobile while the verdict was read, listening mostly with closed eyes.
Jubilation broke out in the tightly packed court room after the judge announced the life sentence and Habre was whisked away by security personnel.
"Habre's conviction for these horrific crimes after 25 years is a huge victory for his Chadian victims," said Reed Brody, a counsel at Human Rights Watch, who has worked with Habre's victims since 1999.
"This verdict sends a powerful message that the days when tyrants could brutalize their people ... are coming to an end," Brody added.
Amnesty International called the verdict "a landmark decision."
"The case sets a new benchmark for efforts to end impunity in Africa," the human rights group said in a statement.
The United States, which supported Chad during Habre's rule as a bulwark against neigbouring Libyan dictator Muammar Gaddafi, also said it welcomed the conviction.
The ruling was "an opportunity for the United States to reflect on, and learn from, our own connection with past events in Chad," said US Secretary of State John Kerry in a statement.
Rights groups estimate that Habre is responsible for the deaths of around 40,000 people during his rule. About 200,000 people were reportedly tortured by his regime.
Habre's case was heard before the Extraordinary African Chambers, a special criminal court set up by the African Union within the Senegalese court system.
The chamber was created in 2013 amid criticism that the International Criminal Court in The Hague has in the past unfairly targeted African leaders.
More than 90 testimonies were heard during the trial, which started in July 2015, after campaigners had fought for more than two decades to bring Habre to justice. The indictment against Habre was almost 200 pages long.
Habre refused to acknowledge the legitimacy of the court. In July, when the trial started, he had to be dragged into the courtroom and did not stand up or respond when called on by the judge. He also shouted the proceedings were a "farce."
In response, the court appointed a new team of lawyers to represent Habre for the remainder of the trial.
After living freely in exile in Senegal for 22 years, Habre was detained in Dakar in July 2013, less than 72 hours after US President Barack Obama - during a visit to Senegal - expressed his support for Habre to be tried.
Habre's arrest had been delayed for years by Senegal's administration, ignoring Belgian courts' efforts to speed up the process and try him in Europe.