Police say Demjanjuk died at a retirement home in Southern Germany. The 91-year-old, who retired from a career as an Ohio autoworker, was deported to Germany in 2009 to stand trial for his service under the Nazi regime.
He was convicted for serving as a low-ranking guard at the Sobibor death camp. He was found guilty on 28,060 counts of being an accessory to murder. His case broke new legal ground in Germany as the first time someone was convicted solely on the basis of serving as a camp guard, with no evidence of involvement in a specific killing.
Demjanjuk had steadfastly maintained that he had been mistaken for someone else - first wounded as a Soviet soldier fighting German forces, then captured and held as a prisoner of war under brutal conditions.
After his conviction in May, Demjanjuk was sentenced to five years in prison, but was appealing the case to Germany's high court. He was released pending the appeal, and died a free man in his own room in a nursing home in the southern Bavarian town of Bad Feilnbach.
The Associated Press contributed to this report.