Ernst Tremmel was accused of 1,075 counts of accessory to murder for his time working at the death camp in German-occupied Poland.
Tremmel worked at the camp from November 1942 to June 1943.
The trial was to have started on Wednesday in the western city of Hanau, where Auschwitz survivors were expected to give testimony.
"All the appointments related to these proceedings have now been cancelled," the regional court in Hanau said in a brief statement. No cause of death was released.
Tremmel served with an SS Totenkopf unit processing the arrival of prisoners at the camp and was allegedly directly involved in three transports, from Berlin, the French city of Drancy, and Westerbork in the Netherlands.
"Among the deportees, at least 1,075 people were cruelly murdered immediately after their arrival at Auschwitz," the Hanau court said when it announced the trial in February.
Because Tremmel was aged 19 or 20 at the time of his alleged crimes, he was to have been tried under juvenile criminal law despite his advanced age.
Because of his frail health, the court had ordered hearings to be limited to four hours per day.
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The legal foundation for prosecuting ex-Nazis changed in 2011 when German authorities convicted former death camp guard John Demjanjuk solely on the basis of his having worked at the Sobibor camp in occupied Poland.
Last July, Oskar Groening, dubbed the "Bookkeeper of Auschwitz", was sentenced to four years in prison for being an accessory to the murders of 300,000 people at the camp.
But the trial of 95-year-old Hubert Zafke, a former Auschwitz medic, was suspended for the second time last month due to his ill health.
A third man, former SS guard Reinhold Hanning, 94, went on trial on 11 February accused of complicity in 170,000 deaths at Auschwitz.
Further investigations are ongoing.
A 93-year-old former guard at Auschwitz has died a week before he was due to stand trial in Germany.