Rabbi Dr. Jacob Itzhak Niemirower (Romanian: Iacob Isaac Niemirower, born March 1, 1872, in Lemberg, then in the Austro-Hungarian Empire, now Lviv, Ukraine – died November 18, 1939, in Bucharest, Romania) was a Romanian Modern rabbi, theologist, philosopher and historian. Allied with reformist trends in Western and Eastern European Judaism, he served as the first Chief Rabbi of Romanian Jewry between 1921 and 1939, and was a member of the Romanian Senate from 1927 until his death.