His family said he died peacefully Saturday after a long illness.
"My husband was a fighter. He fought for the memory of the 6 million Jews who perished in the Holocaust, and he fought for Israel. He waged countless battles for innocent victims regardless of ethnicity or creed," his widow, Marion, said in a statement released by the writer's foundation.
Wiesel, who won the Nobel Peace Prize in 1986, recounted his family being sent to the Nazi concentration camps in his first book, "Night," which was published in France in 1958.
"(He) gave expression through his exceptional personality, and fascinating books about the victory of the human spirit over cruelty and evil. In the darkness of the Holocaust in which our brothers and sisters -- 6 million -- were murdered, Elie Wiesel was a ray of light and greatness of humanity who believed in the good in man," Netanyahu said.
"I was privileged to know Elie and to learn so much from him."
Born in Romania, Wiesel was 15 when he was sent to the Auschwitz concentration camp in Poland with his family in 1944.
The future writer was later moved and ultimately freed from the Buchenwald camp in 1945. Of his relatives, only two of his sisters survived.
Wiesel told CNN last year that Auschwitz was "to this day, a source of shock and astonishment."
Wiesel survived because an older Jew told him to tell the Nazis he was 18, old enough to work.
He told The New York Times he had thought about why he lived and others didn't.
"If I survived, it must be for some reason," Wiesel said in 1981. "I must do something with my life. It is too serious to play games with anymore, because in my place, someone else could have been saved. And so I speak for that person. On the other hand, I know I cannot."
He was a "messenger to mankind"
He broke his silence on his Holocaust experience 10 years after the liberation with the acclaimed memoir "Night," originally published in French as "La Nuit," which has been translated into 30 languages and has sold millions of copies since its publication.
The Nobel peace laureate, who wrote extensively about the horrors he and others endured, said he knew he'd have to write at some point but feared the words would elude him.f
"I'm not sure, by the way, that I did find them," he said. "Maybe there are no words for what happened. Maybe somehow, the Germans ... the cruel killers, have succeeded at least in one way, at least that it deprived us, the victims, of finding the proper language of saying what they had done to us, because there are no words for it."
In 1986 the Nobel committee called Wiesel an important spiritual leader.
In his speech honoring Wiesel, then-chairman Egil Aarvik said: "From the abyss of the death camps he has come as a messenger to mankind, not with a message of hate and revenge, but with one of brotherhood and atonement."
Wiesel spoke of his own guilt in his moving Nobel acceptance speech.
"Do I have the right to represent the multitudes who have perished? Do I have the right to accept this great honor on their behalf? I do not. No one may speak for the dead, no one may interpret their mutilated dreams and visions," he said.
He said he sensed the presence of the tens of thousands of people who died at Buchenwald, and accepted the prize on their behalf and on behalf of his fellow survivors.
Millions of people were touched by "Night" and dozens of other works Wiesel produced. His books were deeply personal. He was honest with his readers about what he went through physically, emotionally, spiritually.
He wrote, "Never shall I forget that night, the first night in camp, which has turned my life into one long night, seven times cursed and seven times sealed. Never shall I forget that smoke. Never shall I forget the little faces of the children, whose bodies I saw turned into wreaths of smoke beneath a silent blue sky. Never shall I forget those flames which consumed my faith forever. Never shall I forget that nocturnal silence which deprived me, for all eternity, of the desire to live. Never shall I forget those moments which murdered my God and my soul and turned my dreams to dust. Never shall I forget these things, even if I am condemned to live as long as God himself. Never."
Throughout his life, the writer and teacher sought to give a voice to the voiceless.
He was a professor at the City College of New York from 1972 until he left four years later to become a humanities professor at Boston University. Before that, Wiesel was a journalist in Paris and then New York.
Michael Zank, the director of the Elie Wiesel Center for Jewish Studies at Boston University, said in an email to CNN that he was "heartbroken at his passing."
"Boston University is losing an iconic teacher who brought an incredible intensity to every encounter with students and colleagues," Zank wrote.
In 1978, President Jimmy Carter appointed Wiesel chairman of the Presidential Commission on the Holocaust. Wiesel's efforts at the commission led to the establishment of the United States Holocaust Memorial Museum in Washington, where his words greet visitors at the entrance. "For the dead and the living, we must bear witness."
He gave a voice
Wiesel was, in the words of the museum, the international leader of the Holocaust remembrance movement.
"In the aftermath of the Holocaust, at a time when the world could not bear to remember, he could not bear to forget," the museum wrote in a statement. "Through his singular moral leadership, intellect, and eloquence, he gave voice to those who had been silenced forever and devoted his life to fulfilling the promise of 'never again' for all future victims of genocide."
Wiesel also didn't shy away from making strong remarks. While at the White House in 1985, he asked President Ronald Reagan to cancel a visit to a World War II military cemetery in West Germany.
"That place, Mr. President, is not your place,'' he said, according to The New York Times. ''Your place is with the victims of the SS.''
Reagan wasn't the only President whom Wiesel pushed to effect change.
"As he often said, one person of integrity can make a difference. For so many, he was that difference, including at the dedication of the Holocaust Memorial Museum in 1993 when he urged me to stop the ethnic cleansing in Bosnia," President Bill Clinton said Saturday.
Elie Weisel's son, Elisha, said the author and activist inspired people to make a difference.
"My father raised his voice to presidents and prime ministers when he felt issues on the world stage demanded action," Elisha Wiesel said. "But those who knew him in private life had the pleasure of experiencing a gentle and devout man who was always interested in others, and whose quiet voice moved them to better themselves."
He wanted peace
When he returned to the site of the Buchenwald death camp in 2009, he advocated for peace in the Middle East while addressing President Barack Obama and German Chancellor Angela Merkel.
He lamented there was no grave of his father to visit and said the hope of no more war that he felt upon his rescue in 1945 was damaged.
"What can I tell him?" he asked. "That the world has learned? I am not so sure."
He implored Obama to help bring peace to the world.
"The time must come. It's enough -- enough to go to cemeteries, enough to weep for oceans. It's enough," he said. "There must come a moment -- a moment of bringing people together."
Wiesel defended the cause of Soviet Jews, Nicaragua's Miskito Indians, Ethiopian-born Israeli youth, Argentina's "Disappeared," Cambodian refugees, the Kurds, and victims of famine and genocide in Africa, apartheid in South Africa and war in the former Yugoslavia, according to the website of the Elie Wiesel Foundation, which he and Marion founded in 1986.
The family said the funeral will be private but there will be a public memorial, though that has yet to be scheduled.
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