Nehemiah Hiyya ben Moses Hayyun (ca. 1650 – ca. 1730) was a Bosnian Kabalist. His parents, of Sephardic descent, lived in Sarajevo, Bosnia (then a part of the Ottoman Empire), where probably he was born, although in later life he pretended that he was a Palestinian emissary born in Safed. He received his Talmudic education in Hebron.
In his eighteenth year he became rabbi of Uskup (The Ottoman Turkish spelling of the city's name during the period referred to in this article is Üsküp - Ottoman Turkish: اسكوب). This position, however, he held only for a brief period. Thereafter he led a wandering life, as a merchant, as a scholar, or as a mendicant. In the guise of a saint he constantly sought adventures of love. From Uskup he went to Palestine, then to Egypt. In 1708 he made his appearance in Smyrna, where he won some adherents willing to help him publish his Mehemnuta de Kulla, and thus secure a rabbinical position for him. In this work he asserted that Judaism teaches a Trinitarian God. This God, he declared, embodies three faces ("parẓufim") – the Ancient of Days ("'Attiḳ"), the Holy King, and the Shekinah. Ḥayyun's own part in this book consists only of two commentaries; the text was anonymously written by a Sabbatean pupil. Leaving Smyrna, Ḥayyun was led to Jerusalem with pomp and ceremony, but the rabbi of Smyrna, who had seen through his pretensions, warned the rabbis of Jerusalem of his heresies. The immediate consequence was that even before his arrival the rabbis of Jerusalem, though they had never read his work, excommunicated him as a "min," and condemned his book to be burned.