His death was confirmed by his son Antoine, a cardiologist.
Mr. Hessel's life had many notable chapters, including a childhood peopled by European intellectuals, an escape from a German concentration camp, and stints as a diplomat at the United Nations and elsewhere.
But he was not widely known until October 2010, when he published "Indignez-Vous!" a 4,000-word pamphlet that urged young people to revive the flame of resistance to injustice that burned in himself and others during World War II, this time in peaceful rebellion against what he termed the dictatorial forces of international capitalism, and to reassert the ideal that the privileged class must help the less fortunate rise.
In particular, Mr. Hessel's diatribe took aim at France's treatment of illegal immigrants, the influence on the news media by the rich, the shrinking social safety net and, especially, Israel's treatment of the Palestinians.
The book, 29 pages (only 14 of text), held together by two staples and released by a two-person publishing house out of an attic office, had an original print run of 8,000. But it struck a chord with young people distressed by the policies of the French president, Nicolas Sarkozy.
It became a popular stocking-stuffer gift at Christmas from left-leaning parents to their children, and it was taken up as a rallying cry by protesters across Europe responding to the economic crisis. Young Spanish activists called themselves "indignados."
Translated into more than a dozen languages, it sold more than three million copies in Europe in less than a year; in July 2011, translated into English, it was published in the United States as "Time for Outrage!" and became a hand-around for participants in the Occupy Wall Street movement.
"When something outrages you, as Nazism did me, that is when you become a militant, strong and engaged," he wrote. "You join the movement of history, and the great current of history continues to flow only thanks to each and every one of us."
In addition to fame, "Indignez-Vous!" brought significant criticism to Mr. Hessel from those who felt his screed was merely indignant and not in any way prescriptive and especially from those who disagreed with his views on Israel and the Palestinians. Mr. Hessel, whose father was Jewish but whose mother was not, said in interviews that he was a lover and defender of Israel, but he was still accused of anti-Semitism.
Stéphane Hessel was born in Berlin in 1917. His father, Franz, a German writer and translator, had lived for many years in Paris, where he met and befriended Henri-Pierre Roché, an artist and writer, and Helen Grund, a German art student, who would become his wife and Stéphane's mother. When the boy was still a toddler, the family returned to Paris, where Helen took up with Roché, and a three-way love affair ensued, becoming the basis for Roché's 1953 novel, "Jules et Jim," later adapted by François Truffaut into the well-known film.
The Parisian society the family joined included the poet André Breton, the sculptor Alexander Calder, and the photographer Man Ray. The artist Marcel Duchamp taught the young Stéphane to play chess. As a teenager, he met Jean-Paul Sartre.
"Sartre came into my life when I was 17, at the time his first novels were published," he said in a 2012 interview for the English-language Israeli Web site Haaretz. "His message was very clear: 'You must devote your responsibility, you become a human being only when you feel your responsibility.' "
In 1941, after France fell to the Nazis and the year his father died, Mr. Hessel escaped to London, where he met Charles de Gaulle, eventually joining the resistance movement. In March 1944, he returned to Paris on a mission to contact underground activists, but was captured and tortured by means now known as waterboarding, surviving, he said, by giving out false information.
He was subsequently sent to the Buchenwald concentration camp, where he escaped hanging by exchanging identities with a French soldier who had died of typhoid fever. Sent to a different camp, he managed to escape and return to Paris, which had by then been liberated.
After the war, Mr. Hessel became a diplomat, working as an official for the newly formed United Nations, where he participated in the drafting of the Universal Declaration of Human Rights, adopted in 1948. He later held diplomatic posts in Algeria and Vietnam.
Mr. Hessel is survived by his wife, Christiane Hessel-Chabry, and three children from an earlier marriage.
Mr. Hessel wrote or contributed to several other books, including a 1997 autobiography, "Danse Avec le Siècle" ("Dance With the Century"). He was a defender of the European Union, and he befriended French politicians of the left, including the current president, François Hollande. Mr. Hollande described Mr. Hessel on Tuesday as "a great figure whose exceptional life was dedicated to defending human dignity."