SIXTUS OF SIENA (1520–1569), Italian convert and anti-Jewish polemist. Sixtus was born in Siena. Shortly after his conversion he entered the Franciscan order and devoted himself to the study of the Bible. After a short while, he was charged with heresy and sentenced to die at the stake. Pope Pius *V saved him and transferred him to the Dominican order. In the Papal States Sixtus and another convert, Filippo Moro, preached the conversion of the Jews and incited the rabble against them. In 1559 he was instrumental in the burning of the Talmud in Cremona. On the other hand, he saved the Zohar from destruction, in the hope that mysticism and Kabbalah would turn the Jews to Christianity. His most important work was Bibliotheca Sancta ex praecipuis Catholicae Ecclesiae auctoribus collecta (Venice, 1566), an introduction to the Bible which includes an alphabetical list of Jewish commentators.
Bollettino senese di storia patria, 14 (1907), 174–83; F. Secret, Les Kabbalistes Chrétiens de La Renaissance (1964), index; Roth, Italy, 302, 303f.