Rafajil Nikolai Korsak (Belarusian: Рафал Мікалай Корсак, Ukrainian: Рафаїл Корсак, Polish: Rafał Mikołaj Korsak) (c. 1599 – 28 August 1640) 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 1620, he entered in the Order of Saint Basil the Great, taking the religious name of Rafajil (Rafael), and passed his year of novitiate in the monastery of Byten.

[3][2] He studied in the Greek College in Rome from December 1621 to November 1624,[4] when he was requested to return to his country to serve as a bishop.

In 1625, Korsak became archimandrite of the monastery of the Holy Trinity in Vilnius (the main monastery of the Order), in 1626 Proto-Archimandrite (i.e. Superior general) of the whole order (an office he kept till 1636) and in September 1626 he was consecrated a bishop with the title of Galicia.

Metropolitan Rutsky chose him as coadjutor bishop with the right of succession, and so he was confirmed by Rome on 9 March 1631 notwithstanding the King's initial concern about his young age.

The new king, Władysław IV, in order to be elected, was compelled to sign the "Pacta Conventa" which was favorable to the Orthodox faction, supported by the Cossacks, and prejudicial to the Greek-Catholic Church.

[7] 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.

In particular, he engaged with Metropolitan Peter Mogila, seeking a way to unify the Church in Ukraine.

[6] However, in 1639, he had to return to Rome for the third time at the request of the pope (visit ad Limina).

[2] He wrote a biography of Metropolitan Rutsky, and he translated in Latin the works of Meletius Smotrytsky.

On Sat Praha-Vilnius, 1981: Florovský Antonín V., Čeští jezuité na Rusi.