MICHAEL, HEIMANN JOSEPH ḤAYYIM (1792–1846), German merchant and bibliophile. Michael was born in Hamburg and lived there all his life. He assembled one of the finest collections of Hebrew manuscripts and books, a library containing 5,471 printed books and 862 manuscripts, of which 60 were autographs and 110 were written between 1240 and 1450. He maintained a lively correspondence, partly in German in Hebrew letters and partly in an attractive Hebrew, with L. *Zunz (in the years 1832–46), S.J. *Rapoport, and S.D. *Luzzatto. This correspondence is a treasury of bibliographical information.
A detailed catalog of Michael's collection, Oẓerot Ḥayyim, with notes by Moritz Steinschneider and an introduction by L. Zunz, appeared in 1848. After Michael's death his friend M. Isler appealed to all friends of Jewish scholarship, wealthy German Jewry in particular, to preserve the priceless collection in Jewish hands and to save it from being sold abroad. The appeal was in vain, and Michael's library was dispersed, the books going to the British Museum in London and the manuscripts, over 860 pieces, to the Bodleian at Oxford (see *Libraries) for a little over £1,000.
Michael's encyclopedic work, Or ha-Ḥayyim (1891; repr. Jerusalem, 1965, with additional notes by N. Ben-Menahem), based on his very rich collection, contains the biographies and bibliographies of medieval Jewish scholars.
A. Berliner, in: JJLG, 4 (1906), 269–74; A. Marx, Studies in Jewish History and Booklore (1944), 221–4 and passim; H. Michael, Or ha-Ḥayyim (19652). ADD. BIBLIOGRAPHY: ADB, vol. 21, 673.