Sabbatai Zevi (Hebrew: שַׁבְּתַי צְבִי; Turkish: Sabetay Sevi; August 1, 1626 – c. September 17, 1676), also spelled Shabbetai Ẓevi, Shabbeṯāy Ṣeḇī, Shabsai Tzvi, Sabbatai Zvi, was a Jewish mystic and ordained rabbi from Smyrna (now İzmir, Turkey). A kabbalist of Romaniote or Sephardic origin, Zevi, who was active throughout the Ottoman Empire, claimed to be the long-awaited Jewish Messiah. He was the founder of the Sabbatean movement.

Upon arriving in Constantinople in February 1666, Sabbatai was imprisoned on the order of the grand vizier Köprülüzade Fazıl Ahmed Pasha. In September of that same year, after being moved from different prisons around the capital to Adrianople (now Edirne), the imperial courts' seat, to be judged on accusations of fomenting sedition. Sabbatai was given the choice of either facing death by some type of ordeal, or of converting to Islam by the Grand Vizier representing the Sultan of the Ottoman Empire, Mehmed IV. He seems to have chosen the latter course, donning a turban from that time on. The heads of the Ottoman state then rewarded him with a generous pension for complying with their political and religious plans. About 300 families who followed Zevi also converted to Islam and became known as Dönme.

Subsequently, the Ottomans banished him twice, first to Constantinople, and, when he was heard singing Psalms with Jews, to a small town known today as Ulcinj in present-day Montenegro. He later died in isolation.