Hypatius Pociej (Belarusian: Іпацій Пацей), Polish: Hipacy Pociej, Ukrainian: Іпатій Потій) (12 April 1541 – 18 July 1613) was the "Metropolitan of Kiev, Galicia and all Ruthenia"[a] in the Ruthenian Uniate Church — a sui juris Eastern Catholic Church in full communion with the Holy See.

[1] In his youth, under the influence of Prince Radziwill, Adam converted to Calvinism, but about 1574, scared about the extremes of that denomination he returned to the Orthodox Church.

They arrived in Rome on 25 November 1595 and obtained the approval of the Pope on the conditions that Byzantine rite, liturgical practices and the not-use of the filioque would be preserved.

[5] Hypatius Pociej was appointed new Metropolitan of Kiev in August 1599 by the will of king Sigismund III Vasa [6] and he was confirmed by Pope Clement VIII on 15 November 1600.

Among his works we have: "The Union, or an Exposition of the Articles" (1595), "Antirysis" (Anti-Discourse, 1599), "A Defense of the Council of Florence" (1603), and "Harmony, or the Agreement of Faiths" (1608).