Former Argentine naval officer Alfredo Astiz has been jailed for life for crimes against humanity during military rule in 1976-83.
Astiz - known as the "Blond Angel of Death" - was found guilty of torture, murder and forced disappearance.
Among his victims were two French nuns and the founders of the Mothers of the Plaza de Mayo human rights group.
Eleven other former military and police officers were also given life sentences for crimes against humanity.
Four others were jailed for between 18 and 25 years.
All worked at the Naval Mechanical School in Buenos Aires - known as Esma - which was the biggest secret torture and killing centre set up by the military during what became known as the "Dirty War".
Of the 5,000 or so prisoners taken to Esma, 90% did not come out alive.
Some were killed by firing squad while others were thrown from planes - drugged but still alive - into the Atlantic Ocean.
More than 70 of those who did make it out were among the witnesses in the 22-month trial.
Symbol of oppression
Astiz looked straight ahead and showed no emotion as the sentence was read out.
Among the others given life terms are Jorge Acosta, Antonio Pernias and Ricardo Cavallo.
Human rights groups had campaigned for years to bring the perpetrators to justice, and there were celebrations as the sentences were read out.
"We resisted. We never committed a crime. This is why this is just. They committed crimes. They are imprisoned," said Esma survivor Ricardo Coquet.
Astiz, 59, is one of the most notorious symbols of oppression during military rule in Argentina.
As a young naval intelligence officer he infiltrated the Mothers of the Plaza de Mayo human rights group, which was set up to find relatives abducted by the security forces.
He then arranged the kidnap and murder of its three founders - Azucena Villaflor, Esther Ballestrino and Maria Ponce.
He had already been convicted in absentia in France for the murder of the French nuns Alice Domon and Leonie Duquet, who disappeared in Argentina in 1977.
In his defence, Astiz said he had acted to save Argentina from left-wing "terrorism", and he dismissed his trial as an act of political vengeance.
Human rights groups say 30,000 people were killed or made to disappear by the armed forces in their campaign against opposition activists and left-wing guerrillas.