Rabbi Moshe Feinstein (March 3, 1895–March 23, 1986) was a Lithuanian Orthodox rabbi, scholar and posek ('decosore" Of Jewish law), who was world-renowned for his expertise in Halakha and was regarded by many as the de facto supreme rabbinic authority for Orthodox Jewry of North America. In the Orthodox world, it is universal to refer to him simply as "Reb Moshe."

Rabbi Feinstein was born, according to the Hebrew calendar, on the 7th day of Adar, 5655 (traditionally the date of birth of the Biblical Moshe) in Uzda, near Minsk, Belarus, then part of the Russian empire.

The son of Rabbi David Feinstein, rabbi of Uzdan, Moshe studied with his father and also in yeshivas located in Slutsk, Shklov and Amstislav, before being appointed rabbi of Lubań where he served for sixteen years. Under increasing pressure from the Soviet regime, he moved with his family to New York City in 1936 where he lived for the rest of his life.

Settling on the Lower East Side, he became the rosh yeshiva of Mesivtha Tifereth Jerusalem. He later established a branch of the yeshiva in Staten Island, New York, now headed by his son Rabbi Reuven Feinstein. Moshe's son Rabbi David Feinstein heads the Manhattan branch.

He was president of the Union of Orthodox Rabbis of the United States and Canada and chaired the Moetzes Gedolei HaTorah of Agudath Israel of America from the 1960's until his death. Rabbi Feinstein also took an active leadership role in Israel’s Chinuch Atzmai.

He was revered by many as the Gadol Hador (greatest Torah sage of the generation), including by Rabbi Yaakov Yisrael Kanievsky, Rabbi Yonasan Steif, Rabbi Elyah Lopian, Rabbi Aharon Kotler, Rabbi Yaakov Kamenetsky and Rabbi Yosef Shalom Elyashiv, even though several of them were far older than he. He was universally recognized as the preeminent Torah sage and Posek of his generation, and people from around the world called upon him to answer their most complicated Halachic questions.

Rabbi Feinstein participated in the Rabbis' march on Washington on October 6, 1943