Rabbi Dr. Hosea Jacobi (born Hosea Hermann Jacoby; 1841–1925) was Chief Rabbi of Zagreb, Croatia for 58 years and the spiritual and religious leader of the Jewish community in Croatia.

He studied Semitic languages, Hebrew and Theology, in the universities of Berlin and Halle, Saxony-Anhalt (Ph.D. 1865, his dissertation being "De loco feminarum apud Iudaeos antiuissimos maxime matrimonii contrahendi ratione habita" – "The Role of Women in Judaism").

Jacobi established and headed, in Zagreb, the Jewish elementary school (Talmud Torah), taught Jewish Studies in high-schools, taught Hebrew and Judaism and established Jewish-Women organizations.

In 1885 Jacobi delivered the first Synagogue-Sermon in the Croat language thus encouraging the integration of Jews into the general population; he also wrote the first ever Jewish-Studies text-books in Croatian.

Jacobi's children: his son Dr. Ivan (Hans, Johanan), his daughters Luise Zaloscer and Klara (Loja) Barmaper and his son-in-law Dr. Hugo Spitzer were among the prominent leaders of the Jewish community and Zionist Movement in Croatia.