Mr Bignone denied the charges
Argentina's former military ruler Reynaldo Bignone has been sentenced to 25 years for human rights abuses committed almost three decades ago.
Gen Bignone, 82, ordered abductions and torture while second in command of the country's largest torture centre between 1976 and 1978.
Relatives of victims held up photos of their loved ones and cheered at the end of the trial in Buenos Aires.
Six officials from the same era were also handed jail terms.
Gen Bignone, who served as de facto president between 1982-83, was found guilty of involvement in 56 cases of murder, torture and kidnappings.
His charges were for crimes committed before becoming leader, when he was in charge of the notorious Campo de Mayo military base.
Campo de Mayo, outside Buenos Aires, is said to have been the largest in operation during the country's seven-year Dirty War, which ended in 1983.
"Justice was slow in coming but it has finally arrived," said Estela de Carlotto, head of the human rights group Grandmothers of the Plaza de Mayo.
Human rights groups say some 30,000 people died or "disappeared" during the period, which saw the military target left-wing opponents.
The trial comes after amnesty laws, which had shielded perpetrators from charges, were overturned in 2005 by the country's Supreme Court.