Anton Anastas Sielava (Belarusian: Антон Анастас Сялява, Ukrainian: Антін Селява, Polish: Antoni Sielawa) (1583 – 5 October 1655) 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.

In 1612 he entered in the Order of Saint Basil the Great, in the monastery of the Holy Trinity in Vilnius,[1] taking the religious name of Anton (Antony).

Rafajil Korsak died in Rome in August 1640 and, according to his last will, Pope Urban VIII confirmed Sielava as new Metropolitan after the usual process of eligibility.

As with his predecessor, he continued to negotiate with the prelates of the Metropolis of Kiev, Galicia and all Ruthenia who remained loyal to the Ecumenical Patriarchate of Constantinople.

[6]: 231  Sielava had to leave Polotsk and died on 5 October 1655,[4] when already (since 1653) the Greek-Catholic Church was in the resolute hands of Gabriel Kolenda.