Cemach Feldstein ([t͡ʃɛɱɑħ fɛldstajn]; sometimes spelled Tzemach; Hebrew: צמח פלדשטיין; Yiddish: פעלדשטיין; Lithuanian: Feldsteinas; Russian: Семён Григорович Фельдштейн, Semyon Grigorovitch; December 30, 1884 - December 29, 1944 was a Lithuanian educator, author, an education reformist, a culture Zionist activist. As an educator he was served as the director of several Jewish gymnasiums, the most notable of which was the Hebrew Real-Gymnasium in Kaunas (Kovno), Lithuania (1922-1940), where most of the subjects were taught in Modern Hebrew.