The Jewish community in Vienna, where Wiesenthal lived, is holding a memorial service today for the Nazi hunter, who died in his sleep yesterday.
Speaking five years ago at the unveiling of a Holocaust memorial in the Austrian capital, Wiesenthal said he had dedicated his life to bringing Nazi officials to justice in order to help prevent the world from experiencing similar horrors in the future.
"For 55 years, more than half of a lifetime, I have fought against forgetfulness," Wiesenthal said. "I believe remembering is very important for preventing a recurrence."
Austrian Chancellor Wolfgang Schuessel, President Heinz Fischer, and Vienna Mayor Michael Haeupl are all due to attend the ceremony at the capital's Central Cemetery. Dozens of foreign ambassadors and relatives are also expected to be present.
U.S. President George W. Bush said in a statement that Wiesenthal had been "a tireless and passionate advocate who devoted his life to tracking down Nazi killers and promoting freedom."
Israel's President Moshe Katsav praised Wiesenthal as the "biggest fighter" of his generation.
Israeli Foreign Minister Silvan Shalom, speaking yesterday at United Nations headquarters in New York, invoked Wiesenthal's memory in calling on the General Assembly to adopt a resolution commemorating the Holocaust.
"Particularly today, the day the world's great Nazi-hunter, Simon Wiesenthal, has passed away, we are reminded that the Holocaust is passing from human memory to history," Shalom said.
Wiesenthal helped track down some 1,100 Nazis, including Adolf Eichmann -- the henchman of Adolf Hitler who was in charge of orchestrating the extermination of Jews.
Wiesenthal always said that his motivation was not revenge, but justice. He rejected the concept of the German nation's collective guilt over the Holocaust.
German President Horst Koehler paid tribute to Wiesenthal, whom he called "a role model."
"Well, that is very sad news, because Simon Wiesenthal is regarded as one of the great ones, who contributed so much to ensure that the crimes of the Nazi era could be discussed, and with an outlook into the future," Koehler said. "He tried to demand his rights and not seek revenge. And I think that should be a role model for us."
Apart from Eichmann, Wiesenthal helped find the Nazi officer responsible for the arrest in Amsterdam of Anne Frank, the Jewish teenager whose diaries are one of the best-known records of the deprivations of the Holocaust era, and who died in Germany's Bergen-Belsen concentration camp in 1945.
Wiesenthal also enabled the capture of Franz Stangl, the commandant of the notorious Treblinka camp in Poland.
However, Wiesenthal was never able to track down one of the most infamous Nazi criminals -- Josef Mengele, who played an instrumental role in the extermination of Jews at Auschwitz.
In 1985, Wiesenthal said he had information that Mengele had died in South America.
"It was last year that an SS man was a witness that Mengele died in 1976," Wiesenthal said. "It was at the beginning of this year also, I think."
Simon Wiesenthal was born in 1908 near Lviv, in what was then the Austro-Hungarian empire. He studied in Prague and Warsaw and in 1932 received a degree in civil engineering.
He survived five Nazi concentration camps and seven other prisons, weighing just 45 kilograms when the U.S. Army liberated the Mauthausen concentration camp in May 1945. Wiesenthal lost 89 relatives during the war.
Wiesenthal founded the Jewish Documentation Center in 1947 and opened an office in Vienna in 1961.
Peter Black, chief historian at the Holocaust Museum in Washington, D.C., praised Wiesenthal for his almost single-handed efforts to track down Nazi war criminals after the war:
"Simon's most important legacy is that he -- acting alone, almost like a Don Quixote -- kept alive the issue of Nazi offenders who had not been called to justice in the 1950s and 1960s at a time when few were interested and fewer still cared," Black said.
Wiesenthal will be buried in Israel on 23 September.
(RFE/RL's Russian Service/news agencies)