R. Samuel Jacob Rabinowitz (1857–1921), Lithuanian rabbi and Zionist leader. Born in Kelme, Rabinowitz held rabbinical posts at Ivye, Aleksot, and Sopotskin and was esteemed as a writer of responsa and novellae, some of which were collected in his Sefer Orah Yashar (1903). An early member of the Hovevei Zion, Rabinowitz attended the Second Zionist Congress, where he made a deep impression on both Theodor Herzl and the delegates; he was elected to the Zionist General Council, later serving as one of the first directors of the Jewish Colonial Trust. In 1899 Rabinowitz led the Lithuanian Zionists in their battle against the Lishkah Shehorah, a group of violently anti-Zionist rabbis. As a result of his vigorous efforts, over 100 East European rabbis wrote letters in support of the Zionist movement. After the Fourth Zionist Congress Rabinowitz accompanied Isaac J. Reines on a mission to the Warsaw area, where their efforts to gain the support of leading hasidic rabbis for the Zionist cause met with some success. In 1906 Rabinowitz was appointed rabbi of Liverpool, where he did much to promote traditional observance and communal harmony, despite the early hostility of more Anglicized members of the local community. Together with Reines, he founded the Mizrachi world movement of religious Zionists in 1902, and he maintained his Zionist activity in England, being elected president of the British Mizrachi organization at its first conference in 1918.

A volume of his essays and addresses, Li-Tekufot ha-Yamim ("The Cycle of Seasons," 1918), was sponsored by Ahad Ha-Am, and a supplementary work, Sefer Yashresh Ya'akov (1925), appeared as Liverpool Jewry's memorial tribute, with a preface written by Rabinowitz's successor, Isser Yehudah Unterman. He inspired the character of "Reb Shemu'el" in Herzl's novel Altneuland.