Simḥah Isaac Luzki (Heb: שמחה יצחק בן משה לוצקי, Rus: Луцкий, Симха Исаак бен-Моисей, Pl: Łucki, Sima Izaak), b. 1716 d. 1760 or 1766 was a qaraim maskil, theologian, kabbalist writer, scholar, bibliographer and spiritual leader, known also as "the Karaite Rashi" and "Olam Ẓa'ir" (the latter meaning literally "microcosm" – acronym based on the gematria of his name). He was born in Lutsk and resided there until 1754, when he moved to Chufut-Qaleh (Crimea) by invitation of the rich patron Mordecai ben Berakhah, one of the heads of the local community, to become the new head of their Madrasa. He was a copyist of early Karaite Jewish manuscripts, and wrote various studies of theology, philosophy, halakhah, and kabbalah. His "Light of the Righteous" (1757) is a history of Karaite Judaism and its literature in which he presented a silsila for the Sevel HaYerushah (the Karaite Jewish "unwritten" version of the Mishna) from Judah ben Tabbai.
In the introduction to most of his works he mentioned that he was the son of Moses son of Simhah, son of Joseph son of Yeshu'a (died in Derazhne in 1649 during the Khmelnytsky Uprising), son of Simḥah, son of Yeshu'a, son of Samuel, of a noble family.