| Konstanty Wasyl Ostrogski | |
| Spouse: | Zofia Tarnowska |
| Issue: | Elżbieta Ostrogska Janusz Ostrogski Katarzyna Ostrogska Konstanty Ostrogski Aleksander Ostrogski |
| Coa: | Ostrogski |
| Noble Family: | Ostrogski |
| Father: | Konstanty Ostrogski |
| Mother: | Aleksandra Słucka |
| Birth Date: | 2 February 1526 |
| Birth Place: | Ostróg, Polish–Lithuanian Commonwealth |
| Death Date: | 23 or |
| Death Place: | Ostróg, Polish–Lithuanian Commonwealth |
| Honorific Prefix: | Saint |
| Kostiantyn Ostrozkyi | |
| Titles: | Right-Believing Prince |
| Venerated In: | Orthodox Church of Ukraine |
| Canonized Date: | 12 July 2008 |
| Feast Day: | 26 February |
Konstanty Wasyl Ostrogski (Ukrainian: Костянтин-Василь Острозький|Kostiantyn-Vasyl Ostrozkyi; Belarusian: Канстантын Васіль Астрожскi; Lithuanian: Konstantinas Vasilijus Ostrogiškis; 2 February 1526 – 13 or 23 February 1608) was a Ruthenian Orthodox magnate of the Polish–Lithuanian Commonwealth, a prince, starost of Volodymyr, marshal of Volhynia and voivode of the Kiev Voivodeship. Ostrogski refused to help False Dmitriy I and supported Jan Zamoyski.
The date of birth of Konstanty Wasyl Ostrogski is disputed. According to some historians he was born around 1524/1525.[1] He was born probably in Turów.[2]
He married in January 1553 in Tarnów.
In the 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 supporting the Orthodox Church (see Union of Brest). He was also a promoter of Eastern Christian culture in the Polish–Lithuanian Commonwealth. Around 1576[3] he established the Ostroh Academy, a wellregarded humanist educational and scholarship institution, with the instruction in Greek, Latin and Old Church Slavonic languages. In 1581, the academy produced and published the Ostroh Bible, the first complete printed edition of the Bible in Old Church Slavonic.[4] [5] While Konstanty Wasyl Ostrogski was the proponent of the Eastern Orthodox religion, his son Janusz Ostrogski converted to Roman Catholicism.
Ostrogski's huge latifundium, or landed estate in the eastern Polish–Lithuanian Commonwealth, consisted of 100 towns and 1300 villages.[6] It was Ostrogski who built Starokostiantyniv Castle.
Ostroh boasted an Orthodox academy, a yeshiva, a mosque, and a Unitarian Church.[7]
He was canonized in the Orthodox Church of Ukraine as a Right-Believing prince.