Julius (Judah David) Eisenstein (November 12, 1854 – May 17, 1956) (Hebrew: יהודה דוד אייזנשטיין) was a Polish-Jewish-American anthologist, diarist, encyclopedist, Hebraist, historian, philanthropist, and Orthodox polemicist born in Międzyrzec Podlaski (known in Yiddish as Mezritch d'Lita), a town with a large Jewish majority in what was then Congress Poland. He died in New York City at the age of 101.