Rudolf Kastner (1906–1957) was a Jewish-Hungarian journalist and lawyer who became known for helping Jews escape Nazi-occupied Hungary during the Holocaust. Notwithstanding his successful rescue of almost 1,700 Jews, he was assassinated in 1957 after being accused by an Israeli court of having collaborated with the Nazis.

Kastner was one of the leaders of the Va'adat Ezrah Vehatzalah —the Aid and Rescue Committee, or Vaada— a small Jewish group in Budapest who helped Jewish refugees escape from Nazi Europe into Hungary during World War II, then helped them escape from Hungary after the Nazis invaded that country on March 19, 1944. Between May and July 1944, Hungary's Jews were being deported to the gas chambers at Auschwitz at the rate of 12,000 people a day—for "resettlement," as the Nazis said. Kastner negotiated with Adolf Eichmann, a senior SS officer, to allow 1,685 of them to leave instead for Switzerland, in exchange for money, gold, and diamonds, on what became known as the Kastner train.

Kastner moved to Israel after the war, becoming a spokesman for the Ministry of Trade and Industry in 1952. In 1953, he was accused in unusually strong language of having been a Nazi collaborator, in a pamphlet self-published by Malchiel Gruenwald, an amateur writer and stamp collector. The allegation stemmed in part from Kastner's relationship with Eichmann, and in part from his having given positive character references after the war to three other SS officers, including Kurt Becher, allowing Becher to escape prosecution for war crimes. The Israeli government sued Gruenwald for libel on Kastner's behalf, resulting in a trial that lasted two years, and a ruling in 1955 that Kastner had indeed, in the words of the judge, "sold his soul to the devil." By saving the Jews on the Kastner train, while failing to warn others that their resettlement was in fact deportation to the gas chambers, Kastner had sacrificed the mass of Jewry for a chosen few, the judge said. The verdict triggered the fall of the Israeli Cabinet.

Kastner resigned his government position and became a virtual recluse, telling reporters he was living with a loneliness "blacker than night, darker than hell." His wife fell into a depression that left her unable to get out of bed, while his daughter had to endure her school friends throwing stones at her in the street. The Supreme Court of Israel overturned most of the judgment in January 1958, stating in a 4-1 decision that the lower court had "erred seriously," but not before Kastner had been assassinated. He was shot on March 3, 1957 by Zeev Eckstein, and died of his injuries twelve days later.