Moses Mielziner (August 12, 1828 in Schubin, Grand Duchy of Posen, Prussia - February 18, 1903 in Cincinnati) was an American Reform rabbi and author.
Mielziner received his first instruction in Talmudic literature from his father, Benjamin, who was the rabbi of his native town. At the same time, he received his secular education from L. I. Braunhart. In 1843, Mielziner was sent to Exin, where he attended the yeshiva of the aged rabbi Wolf Klausner, and in 1845 he went to Berlin in pursuit of further secular education, attending at the same time the Talmudic course of Rabbi J. J. Oettinger.
In 1848, having prepared himself privately for academic studies, he entered the University of Berlin. He remained there until 1852, when Samuel Holdheim, who took a great interest in him, recommended him to Waren in Mecklenburg as teacher and preacher. The Orthodox reaction introduced by the "Landrabbiner" Baruch Isaac Lipschütz in 1853 forced Mielziner, much to the regret of his congregation, to resign his position.
He then went to Denmark, where his brother Solomon was minister in Aalborg, and soon obtained a position at Randers in 1854. In 1857 he was called as principal of the religious school to Copenhagen, where he remained until 1865, when he was called to the rabbinate of the Congregation Anshe Chesed in New York City ("New Yorker Staats-Zeitung," 1865, No. 215). When this congregation was absorbed by the Beth-El congregation, he opened a private school, which he conducted until 1879, when he received a call as professor of Talmud and rabbinical literature from the Hebrew Union College in Cincinnati. Upon the death of Isaac Mayer Wise March 26, 1900, he became president of this institution, and held this position until his death.