The Amsterdam-based Sobibor Foundation said Monday that Schelvis died Sunday evening.
Schelvis, who was deported to Sobibor in 1943, lost 18 relatives at the camp in Nazi-occupied Poland.
He wrote several books about Sobibor and founded the Sobibor Foundation in 1999 to keep alive the memory of the camp.
In 2009, he recalled his Sobibor experiences in the Munich trial of Demjanjuk, who was accused of serving as a guard there.
Demjanjuk, a retired Ohio autoworker, was convicted of 27,900 counts of accessory to murder but always denied serving as a guard. He died before his appeal could be heard.