R. Jacob b. Hayyim Zemah (d. after 1665), kabbalist and physician. A member of a Converso family in northern Portugal, he first served as a physician. He decided to go to Erez Israel and passed through Salonika where he studied Torah. Some time between 1610 and 1620, he settled in Safed and learned Talmud and Kabbalah. In approximately 1628 he left for Damascus, and studied the Lurianic Kabbalah under R. Samuel b. Hayyim Vital. Around 1640 he settled in Jerusalem where he became one of the leading kabbalists. He was among the Jerusalem opponents of Shabbetai Zevi who excommunicated him when he first claimed to be the messiah in 1665. His commentaries and works have been appended to later editions of the Zohar.