Kor, a Jewish native of Romania, was sent to the infamous Auschwitz concentration camp in 1944, where most of her family was killed.
Kor and her twin sister, Miriam Mozes Zeiger, survived but were subjected to inhumane medical experiments by Nazi doctor Josef Mengele before they were rescued in 1945.
Zeiger died in June 1993.
A longtime resident of Terre Haute, Indiana, Kor preached forgiveness, even to the Nazis who tortured her and her sister.
She spent the past 40 years sharing her story with students, teachers, doctors, senators, historians and civic groups both nationally and internationally.
In 1995, Kor opened the CANDLES museum to prevent prejudice and hatred through education about the Holocaust. In 2003, the museum was destroyed by an arsonist. Kor vowed to rebuild and, with the public's help, reopened the museum in 2005.
"Eva Kor has touched hundreds of thousands of people over her 85 years through her message of overcoming tragedy, finding forgiveness, and healing," the CANDLES museum said in a statement. "We hope Eva's story continues to change the lives of those who hear it for many years to come."
Museum officials said the center will be closed until Tuesday in honor of Kor's memory.
In 2017, Indiana Gov. Eric Holcomb awarded Kor the Sachem Award, the state's highest honor.
Holcomb tweeted Thursday that "the world just lost a giant."
"Everywhere she went, Eva brought light into darkness & provided comfort to those in pain, unlike anyone we've ever met. From her against all odds survival as a young girl in Auschwitz to her peace-spreading message based from home in Terre Haute, Indiana, her relentless and optimistic example inspired the world. Her angelic spirit will live on in the countless souls she saved from ongoing confusion and torment," Holcomb tweeted.
A public memorial service will be planned.