Irving (Yitzchak) Greenberg (born 1933), also known as Yitz Greenberg, is a Modern Orthodox rabbi, Jewish-American scholar and author. He is known as a strong supporter of Israel and a promoter of greater understanding between Judaism and Christianity. In 1953 Greenberg was ordained at Yeshiva Beis Yosef. He earned a PhD. from Harvard University and served as the Jewish chaplain of Brandeis University, the rabbi of the Riverdale Jewish Center, an associate professor of history at Yeshiva University, and as a founder, chairman, and professor in the department of Jewish studies of the City College of the City University of New York. He has also served as the President of the National Jewish Center for Learning and Leadership. He is married to the Orthodox Jewish feminist writer Blu Greenberg.