Rabbi Leo Jung (Hebrew: Eliyahu; June 20, 1892 – December 19, 1987) was one of the major architects of American Orthodox Judaism.

His father, Meir Tzvi Jung held rabbinic post in Mannheim then was elected rabbi of Uherský Brod in 1890.

Jung's father founded schools in Uherský Brod, Kraków and London, where both religious and secular learning took place.

Jung became the editor of this bi-monthly journal, which he claimed expressed his father's philosophy, "study is great, for it leads to (right) action".

Jung claimed that he received three rabbinic ordinations, from Mordechai Zevi Schwartz, Abraham Isaac Kook and David Zvi Hoffmann of Berlin.

In Cleveland he was an, "utterly novel phenomenon, the first English speaking Orthodox rabbi, bearded and a Ph.D." He saw a weak adherence to a dying Orthodoxy there, which he tried to revive.

Coupled with the inability of the rabbis to discuss this all-important subject and with a lack of informed rebellion among women (who should have refused to get married before the community established decent mikvaoth) the situation prevailed which rendered such hostility on the part of the half informed and uninformed young women more intelligible.Jung was involved in raising standards by actively creating commissions to improve observance of most aspects of Jewish ritual life including circumcision, conversion, kashrut, shabbat, burial, and mikveh.

Since Orthodoxy was not well represented in the Jewish-American publication world, Jung's Jewish Library Series and his other works played an important role in creating books for and about Orthodox Judaism.

[1] The multi-volumed series helped promote traditional rabbinic biography and literature among the American public, though they had limited circulation.

As vice president of the UOJCA and organizer of its Rabbinic Council, Jung and others began a crusade to fight the corrupt "kashrut jungle" and replace it with a reliable system under the OU imprint.

Jung was chairman of the American Beth Jacob Committee, founded to support schools for European Orthodox Jewish girls formed in 1927.

[1] Run by Agudath Israel, the movement was founded by Sara Schenirer, with the help of some leading Western European Jews, to provide an education for girls.

His Israel affiliation was with Poalei Agudat Yisrael, which was called "a fortress of religious Jewry" by some but fiercely opposed by the leading Haredi rabbis of the time.

[1] Reverence for God and man was essential to ensure righteousness or justice, which includes the assurance of our personal worth and of human dignity.

Jung wrote: The key to Judaism is "kedushah" (holiness), the endeavor to plant heaven on earth through divine values.

Rahamanut is usually translated as "mercy" or "compassion" but etymologically it means "mother's love"—the unselfish dedicated love of a mother for her little one, her passionate desire to spend herself ... for the purpose of raising her baby from helpless infancy towards self sufficient maturity.Jung advocated civil rights, avoiding nuclear disaster, and the fighting of the immorality of communism.

His speeches from the 1950s are against segregation, against atomic energy, in favor of the United Nations wanting to bring world peace, racial and economic justice in America.

During these years, he was on the Executive Committee of the Rabbi Samson Raphael Hirsch Society, whose goal was to translate works by German Orthodox thinkers into English.

The ghetto conditions of Eastern Europe and the lower East Side of NYC make the true vision of Judaism hard to be heard.

This dialogue culminated in Wouk publishing This is My God: The Jewish Way of Life in 1959, an introduction to Orthodox Judaism for an American audience.

His grandchildren and great-grandchildren can be found under the family names Etra, Jick, Kassel, Nudelman, Rosen, Rosenfeld, Houminer, Villa, Yoeli and Rubinstein.