Moshe Feinstein was a Russian-born American Orthodox Jewish rabbi, scholar, and posek. He has been called the most famous Orthodox Jewish legal authority of the twentieth century and his rulings are often referenced in contemporary rabbinic literature. Feinstein served as president of the Union of Orthodox Rabbis, Chairman of the Council of the Moetzes Gedolei HaTorah of the Agudath Israel of America, and head of Mesivtha Tifereth Jerusalem in New York.

A rabbi is a spiritual leader or religious teacher in Judaism. One becomes a rabbi by being ordained by another rabbi—known as semikha—following a course of study of Jewish history and texts such as the Talmud. The basic form of the rabbi developed in the Pharisaic and Talmudic eras, when learned teachers assembled to codify Judaism's written and oral laws. The title "rabbi" was first used in the first century CE. In more recent centuries, the duties of a rabbi became increasingly influenced by the duties of the Protestant Christian minister, hence the title "pulpit rabbis", and in 19th-century Germany and the United States rabbinic activities including sermons, pastoral counseling, and representing the community to the outside, all increased in importance.