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Hayyim Mordecai Margolioth (d. 1818) (Hebrew: חיים מרדכי מרגליות) was a Polish rabbi, brother of Ephraim Solomon Margolioth. Ḥayyim Mordecai was at first rabbi at Brestitzki, and later became rabbi in Great Dubno, where he established a printing-office. He was among those who elected the three deputies sent to St. Petersburg to confer with the government upon Jewish affairs, and was the author of Sha'are Teshubah, commentary to Shulḥan 'Aruk, Oraḥ Ḥayyim (Dubno, 1820); it contains extracts from other works and appears in most editions of the Shulḥan 'Aruk. He died at Dunajowce in 1818.