OSTROGSKI, KONSTANTIN VASILIJ. - Prince of Ostrog, b. 1526, d. 1608. Master of vast estates in Podolia, Galicia, and Volhynia and *voivode* (governor) of Kiev, O. was one of the most powerful magnates of the Polish-Lithuanian state. Like his father Constantine before him, he was a patron of the dissident Church and sought to elevate the cultural-religious level in collaboration with Prince Andrei Kurbskii and other refugees from Russia.
To this end, he founded at Ostrog a school for the teaching of classical languages and the liberal arts. In the attached printing house, the first complete edition of the Bible in Church Slavonic was published in 1581. At that time, some dissidents conceived the idea of union with the Catholic Church in order to better confront the common danger of Protestantism, and O. at first did not show himself opposed. When, however, the dissident bishops entered into concrete negotiations with Rome, O. opposed them, perhaps also out of resentment that he had not been consulted beforehand. He therefore did not accept the union concluded at Brest (1596) and until his death supported the dissident bishops, which greatly hindered the consolidation of the union. However, his two sons Janusz and Andrei converted to the Catholic Church during their father’s lifetime.