OSTROG (Heb. אוסטרהא, אוסטרא), city in Rovno district (Volhynia), Ukraine; formerly in Poland. Evidence of the beginnings of Jewish settlement in Ostrog dates from the 15th century; inscriptions on two Jewish tombstones in the ancient cemetery date from 1445, and the archives of Lvov contain
Ostrog was one of the most important centers of Jewish religious learning in Poland, its name being interpreted in Hebrew as Os Torah ("the letter of the Law"). Some of Poland's most eminent scholars served as rabbis and principals of the Ostrog yeshivah, which was already in existence by the beginning of the 16th century. The first-known rabbi of the congregation and principal of the yeshivah was Kalonymus Kalman Haberkasten. Among his notable successors were Solomon *Luria (Maharshal), Isaiah *Horowitz, author of Shenei Luḥot ha-Berit (first quarter of the 17th century), Samuel *Edels (Maharsha), and *David b. Samuel ha-Levi (Taz). According to the last, the Ostrog yeshivah was probably the greatest in Poland: "Never have I seen so important a yeshivah as this." Ostrog was the "great town of scholars and writers" according to Nathan Nata *Hannover. The yeshivah was restored soon after the Cossack destruction through the efforts of Samuel Shmelke, who loaned a large sum to the Council of the Four Lands for its reestablishment and the maintenance of students. Its rabbis included many distinguished scholars and its graduates provided rabbis, principals of yeshivot, dayyanim, and maggidim for numerous communities. Ostrog also became celebrated as a center of *Ḥasidism which was disseminated there by several disciples of *Israel b. Eliezer (the Ba'al Shem Tov). A number of benevolent societies and foundations functioned in Ostrog, the most important being the burial society. During the Russian rule the Jewish population grew from 1,829 in 1787 to 7,300 (including nearby settlements) in 1847, and 9,208 in 1897 (total population – 14,749). Jews were active in the trade of lumber, cattle, and farm products. They owned sawmills, hide-processing and furniture factories, and two banks. After World War I Ostrog turned into a border town within Poland, and was cut of from the Eastern market. This led to an economic decline. The number of Jews fell to 7,991 (total population – 12,975) in 1921, and 8,171 (total population – 13,265) in 1931. The Zionist movement and the Bund flourished. There was a Hebrew elementary and junior high school, and a kindergarten.
M.M. Biber, Mazkeret li-Gedolei Ostraha (1908); Arim ve-Immahot be-Yisrael, 1 (1946), 5–40; Halpern, Pinkas; Pinkas Ostrah: Sefer Zikkaron li-Kehillat Ostraha (1960). ADD. BIBLIOGRAPHY: Pinkas ha-Kehillot Poland, vol. 5 –Volhynia and Polesie (1990).