Bishop Cyril S. Terlecki (Ukrainian: Кирило Терлецький, Kyrylo Terletsky; Belarusian: Кірыла Цярлецкі, Kiryla Ciarlecki; Polish: Cyryl Terlecki; died May 1607) was a religious and political figure and one of the initiators of the conclusion of the Union of Brest in 1596. He served as the Eparch of the Eparchy of Lutsk–Ostroh as both an Eastern Orthodox and Ruthenian Catholic.