Konstanty Wasyl Ostrogski

Konstanty Wasyl Ostrogski (2 February 1526 – 13 (23) February 1608, Канстантын Васiль Астрожскi Konstantinas Vasilijus Ostrogiškis ) was a magnate of the Polish-Lithuanian Commonwealth, a prince, starost of Volodymyr-Volynskyi, marshal of Volhynia and voivode of the Kiev Voivodeship. Ostrogski refused to help False Dmitriy I and supported Jan Zamoyski.

In 1570s he waged a war against another magnate, Stanisław Tarnowski, about disputed possession of estates in the area of Tarnów, in Lesser Poland.

Prince Ostrogski was of Eastern Orthodox faith and he was active in protecting the rights of the Orthodox Church (see Union of Brest) and promoting the culture of the Christian Orthodox religion in the Polish–Lithuanian Commonwealth. In 1576 he established the Ostroh Academy, a highly regarded humanist educational and scholarship institution, with the instruction in Greek, Latin and Old Church Slavonic languages. In 1581 the Academy produced and published the Ostrog Bible, the fundamental Orthodox Bible.

Ostrogski's huge latifundium, or landed estate in the eastern Polish–Lithuanian Commonwealth, consisted of 100 towns and 1300 villages. It was Ostrogski who built Starokostiantyniv Castle.

While Konstanty Wasyl Ostrogski was the guardian of the Eastern Orthodox religion, ironically, his son Janusz-Ivan converted to Catholicism.

He got married on January 1553 in Tarnów.