The Washington Post reports that Videla died at a prison near Buenos Aires.
He was pronounced dead at 8:25 a.m. after he was found in his Marcos Paz prison bed. The cause of death has not yet been announced.
Videla came to power as acting president of Argentina in 1976 in a coup that ousted Isabel Perón. As president, Videla oversaw a series of human rights violations that turned his rule into the bloodiest period Argentina has seen in the modern era. He remained president until 1981.
Videla was prosecuted for crimes including kidnappings, forced disappearances and torture of supposed leftist guerrillas. What became called the dirty war left between 13,000 and 30,000 Argentinians missing, tortured or dead. There were 9,000 documented deaths. Human rights groups suspect the real number may be up to 30,000.
Leftist sympathizers were thrown from planes into the Atlantic Ocean or River Plate to drown. Many others were buried in mass graves. Videla ran concentration camps and torture centers to rid Argentina of the "subversive." Children were snatched from their mothers and given to military families.
Even in interviews last year, Videla stood by his actions, saying that the ones that went missing were "traitors to the cause." He told an Argentine journalist that "there was no other alternative" to reaching his goals.
Videla was sentenced to 50 years in prison for his scheme to steal babies from detained parents on July 5, 2012. The court decision said Videla was an accomplice "in the crimes of theft, retention and hiding of minors, as well as replacing their identities."
A 2009 ruling determined Videla would not receive a military funeral because of his human rights crimes.