Elijah Mizrachi (Hebrew: אליהו מזרחי) (c. 1455 – 1525 or 1526) was a Talmudist and posek, an authority on Halakha. He is best known for his Sefer ha-Mizrachi, a supercommentary on Rashi's commentary on the Torah. He is also known as Re'em (רא״ם), the Hebrew acronym for "Rabbi Elijah Mizrachi", coinciding with the Biblical name of an animal, sometimes translated as "unicorn".
Mizrachi was born in Constantinople; he was of Romaniote origin, meaning that his family was from Ottoman Greece, and not from the Spanish exile. He studied under Elijah ha-Levi and Judah Minz of Padua. As a young man, he distinguished himself as a Talmudist, yet he also studied the secular sciences, particularly mathematics and astronomy; he is said to have been the first to derive a method for the extraction of the cube root. He also knew Greek and Arabic.
Mizrachi succeeded Moses Capsali (on his death c. 1495) as Hakham Bashi ("Grand Rabbi") of the Ottoman empire; he held this position for the rest of his life. As Hakham Bashi he was known for his mild attitude toward the Karaites, an attitude inherited from his teacher Elijah ha-Levi; he even held that it was permissible to teach them Talmud.