Union of Brest
Previously an Eastern Orthodox eparchy headed by a suffragan bishop of the Kiev Metropolitan in Vilnius, in 1596 the eparchy of Polotsk, entered in full communion with the Catholic Church as a Greek Catholic Church through the Union of Brest. The eparchy was among the first that joined the union in 1596 along with eparchies of Kiev, Pinsk, Lutsk, Volodymyr and Kholm. Due to the Union of Brest, Belarus, the former Orthodox Church became known as the Ruthenian Uniate Church.