Jean de Menasce (1902–1973) was a French Catholic priest, of the Dominican Order, as well as an author and academic. He came from Jewish Egyptian and French parentage. Over his lifetime he mastered fifteen languages, including Hebrew, Syriac, and Pahlavi. He was in the Catholic contingent among Jewish and Protestant leaders at an important post-war interfaith conference. Menasce wrote as a theologian, and as a scholar of Middle Eastern studies, especially regarding Judaism, and the Zoroastrian religion.

Jean de Menasce was born in Alexandria on 24 December 1902 into a well-established family in the Jewish community of Egypt. His father, Baron Félix de Menasce, a banker with Austro-Hungarian links, was head of the Jewish community in Alexandria; he had been raised to the peerage by the Emperor of Austria. Jean's mother was French from a Spanish line. A cousin of Jean de Menasce was the writer and diplomat Georges Cattaui, six years his senior. A second cousin was the composer and pianist Jacques de Menasce.

After the local lycée français, Jean de Menasce remained in Cairo studying at its French School of Law. Thereafter he continued his education in Europe, at Oxford University and at the Sorbonne. During the course of his student years, de Menasce had left behind his religious beliefs.

At Oxford's Balliol College, he was a classmate of the future novelist Graham Greene, who also would convert to Catholicism in 1926. Menasce translated into French works of the English poet T. S. Eliot, a friend. In 1922 he made the French translation of a book by the philosopher Bertrand Russell, whom he knew as a fellow member of Lady Ottoline Morrell's salon at Oxford. From the poetry of John Donne, the 17th-century Anglican priest, he had also made French versions. Thus he already enjoyed some recognition when in 1926 he became a convert to Catholicism.

In the meantime, de Menasce had continued to study law and philosophy at the Sorbonne in Paris. Then, while pursuing his interest in Zionism, Chaim Weizmann, a family friend and future President of Israel, appointed him secretary of the Zionist Bureau in Geneva. He then traveled to Jerusalem.

Returning to Paris, de Menasce entered a period of personal spiritual crisis, and painful growth. He began his lifelong friendship with the Catholic philosopher Jacques Maritain and his Jewish wife Raissa, both converts from agnosticism twenty years earlier. Another decisive new friend was Louis Massignon, a scholar whose 4-volume study of the Islamic mystic Al-Hallaj had just been published. Massignon, also a convert, had met de Menasce at the La Revue juive [The Jewish Review].

In this learned milieu, in an atmosphere of intense spiritual awareness, de Menasce converted. During his inquiring approach to Christianity with Massignon he had discussed the mystics Theresa of Avila and Francis of Assisi. He had also followed the modern naisance of Jewish-Christian dialogue. After his baptism he spent the first months writing his book on Hassidism, Quand Israel aime Dieu. According to Adrian Hastings:

The book was "an exceptionally beautiful study of Jewish Hasidic holiness. It was, in a way, his farewell tribute to the religion of his ancestors, but one feels that he was able to make it only after he had rediscovered the God of Israel through the discovery of Jesus as Messiah."