Erich Priebke, the last survivor of the Nazi military officers convicted over one of Italy's worst wartime atrocities, died on Friday in Rome at the age of 100, his lawyer said.
Priebke, who never apologized for his role in the killing of 335 civilians in 1944, was serving out a life sentence under house arrest.
"Priebke never had time for even a moment of emotion for the family members of his victims. It would have cost him nothing but he never did it," said Riccardo Pacifici, the president of Rome's Jewish community.
"Now he will be judged by those he killed."
Priebke, who called himself "the last prisoner of war," was extradited to Italy in 1995 from Argentina and definitively convicted in 1998 after several appeals.
The Ardeatine Caves Massacre - a mass execution of civilians on March 24, 1944 - is etched in Italy's national psyche. Presidents, popes and heads of state have visited the site to pay homage to the victims.
The executions in the caves south of Rome were carried out as a reprisal for a partisan bomb attack that killed 33 German soldiers on a Rome street the day before.
Hitler ordered occupation forces to respond within 24 hours by executing 10 Italians for each German killed.
The victims, who eventually numbered five more than had been ordered by Hitler, were rounded up from jails and also taken from streets and homes and brought to the caves.
Priebke, then an aide to the Gestapo chief in Rome, Herbert Kappler, admitted to helping draw up a list of victims, ticking their names off as they were killed, and to personally shooting two of them.
The victims included 75 Jews and the youngest was a 15-year-old boy. The German officers shot the victims in the back of the head in groups of five and later blew up the caves in an attempt to hide the massacre.
Kappler, Priebke's superior, was sentenced to life in prison in 1947, escaped from a prison hospital in Italy in 1977 and died a year later in Germany. Karl Hass, another officer who was convicted along with Priebke, died in 2004.
Priebke was first tried by an Italian military court in 1996 but it ruled that he could not be held because of the statute of limitations. Protesters occupied the court building and he was re-arrested after eight hours.
A second trial in 1997 convicted and sentenced him to 15 years and the next year an appeals court sentenced him to life in prison. He was later granted house arrest because of his advanced age.
Before his extradition to Italy, Priebke had been living a tranquil life since 1949 in the Argentine mountain resort town of Bariloche along with other former Nazis.
He was tracked down there in 1995 by an American television journalist. He admitted his role in the massacre but said he was carrying out orders and that he and his German comrades at the time were responding to an attack by "terrorists".