MUELLER, JOEL (1827–1895), rabbinical scholar and authority on geonic texts. Born at Maehrisch Ostrau, Moravia, Mueller received his early talmudic education from his father, rabbi in Maehrisch Ostrau, whom he succeeded in 1853. After a period as rabbi in Leipa, Bohemia, and as a teacher of religion in Vienna, in 1884 he began teaching at the Berlin Hochschule fuer die Wissenschaft des Judentums.
Mueller published a series of rabbinic texts, chiefly responsa, of the geonic and immediate post-geonic period, which are models of scholarly editions. The most important are the post-talmudic tractate Massekhet *Soferim (1878), with an introduction and copious notes in German; a post-talmudic work on ritual differences between Ereẓ Israel and Babylon, Hilluf Minhagim (in Ha-Shaar 7 (1876), and 8 (1877); published separately, 1878); Teshuvot akhmei arefat ve-Loter ("Responsa of French and Lorraine Scholars," 1881, repr. 1959, 1967); Teshuvot Ge'onei Mizrah u-Ma'arav ("Responsa of Eastern and Western Geonim," in Bet Talmud, 4 (1885); and 5 (1886); published separately 1888; repr. 1959, 1966); Mafte'a li-Teshuvot Ge'onim ("Introduction to Geonic Responsa," 1891; repr. 1959); and Halakhot Pesukot ("Short Geonic Responsa," 1893). Mueller also edited Saadiah's "Book (on the law) of Inheritance," Traité des Successions…, for J. Derenbourg's edition of Saadiah's writings (Oeuvres Complètes; vol. 9, 1897). For the annual reports of the Lehranstalt he published studies on responsa in the pre-geonic period (in: 4, 1886); on those of tenth-century Spanish teachers (in: 7, 1889); on Yehudai Gaon (in: 8, 1890), and on the responsa of Meshullam b. Kalonymus (in: 11, 1893); see also his Responsa of Kalonymos of Lucca (Teshuvot Rabbenu Kalonymos mi-Lucca, 1891).
M. Schreiner, Gedaechtnisrede auf Joel Mu eller (1896); Bericht ueber die Lehranstalt fuer die Wissenschaft des Judentums, 15 (1897), 32ff.; S. Federbush, Ḥokhmat Yisrael be-Eiropah (1965), 402.