Athanasius (Filippovich) was born around 1597 in the Grand Duchy of Lithuania to a Ruthenian family. He undertook the Orthodox monastic vocation at the Kupiatych Monastery in the late 1620s.
During the period of the Union of Brest (1596) — the Vatican-Polish union that had created the Uniate (Greek Catholic) Church from the Kievan Metropolitanate — Athanasius undertook the mission of defending the Orthodox tradition against the Polish-Uniate coercion.
Athanasius travelled to Moscow (1638) to seek Muscovite Russian Orthodox support for the Belarusian-Ukrainian Orthodox community, and to Warsaw (1643) to personally petition King Władysław IV of Poland.
During the Khmelnytsky Uprising of 1648 (the Ukrainian Cossack revolt against Polish rule), Athanasius was arrested by Polish authorities at Brest. On September 5, 1648, Athanasius was shot by Polish soldiers at Brest.
Canonized in 1666 by the Council of Moscow.

