Konstanty Wasyl Ostrogski (c. 1520–1608) was a prominent Ruthenian politician and a powerful magnate within the Grand Duchy of Lithuania and the Polish-Lithuanian Commonwealth. Born in Turov, he held numerous influential positions, including serving as the voivode of Kyiv for nearly five decades. As a leading figure of the Eastern Orthodox faith, he dedicated much of his life to defending its interests and supporting its institutional growth during a period of significant religious tension.