Klestil, whose second six-year term was to end Thursday, died shortly before midnight from multiple organ failure, officials at Vienna's General Hospital told The Associated Press. He had been taken to hospital by air on Monday after suffering heart failure (search).
Heinz Fischer, who won elections earlier this year, takes over the presidency on Thursday. Chancellor Wolfgang Schuessel assumed the presidential duties when Klestil fell ill.
Earlier in the day, Dr. Christoph Zielinski said the president's liver, lungs, kidneys and central nervous system had been damaged by the cardiac problem.
When he was admitted on Monday, doctors said they could not rule out brain damage (search) as a possible result of lack of oxygen before hospital staff got his heart functioning again.
Hospital director Reinhard Krepler said Klestil was surrounded by his family when he died.
Klestil was widely credited with restoring Austria's credibility following revelations that predecessor Kurt Waldheim served in Germany's Nazi military.
Klestil distinguished himself by speaking out numerous times against Austria's Nazi complicity during World War II, expressing sympathy for Holocaust victims during a first-term visit to Israel.
And though Austria's presidency is a largely ceremonial post, he strengthened the country's ties with emerging democracies in Eastern Europe and in 1993 began convening a yearly meeting of the heads of state of Central European countries.
But he later found himself roiled in political turmoil as he feuded with the rightist Freedom Party, which gained popularity with its anti-immigrant, populist rhetoric.
Though nominated for the presidency by Austria's conservative People's Party, Klestil later clashed with its leader, Chancellor Wolfgang Schuessel, and was abandoned by the party. Political differences between the two included Klestil's opposition to letting the Freedom Party join the party in forming a coalition government in 2000.
Klestil backed off. But front-page photos of a stone-faced Klestil swearing in members of the Freedom Party to government posts spoke volumes about his opposition to letting those linked to anti-foreigner and past anti-Jewish sentiment share government responsibility.
Critics occasionally accused Klestil of overstepping the ceremonial bounds of his office. But he proved an efficient president, and in 1995, during his first term, Austria joined the European Union.
When the European Union punished Austria for allowing the Freedom Party to join the government, he put his diplomatic skills to work and lobbied heads of states to lift sanctions seven months after they were slapped on the nation.
The Viennese-born Klestil studied economics and business before earning a doctorate in 1957. In 1969, he established the Austrian General Consulate in Los Angeles, where he befriended Arnold Schwarzenegger, the Austrian bodybuilder who went on to become a movie star and is now the governor of California.
In 1978, he was appointed Austria's ambassador to the United Nations. Four years later, he moved to Washington, where he became the Alpine nation's ambassador to the United States.
He was elected president in 1992, succeeding Waldheim, the former U.N. secretary-general who was widely despised following revelations that he had concealed details about his service in the German army during World War II.
Klestil was re-elected but was barred by the constitution from running for a third term.
He is survived by his wife, and a daughter and two sons from a previous marriage. Funeral arrangements were not immediately available.