1617
Ordo S. Basilii Magni / The Order of St Basil the Great

The Rule of St Basil (329–379) is the basis of Eastern Christian monastic life. After the 1596 Union of Brest, it was applied to the Eastern Rite Catholic Monastic Order, which emerged in the Grand Duchy of Lithuania in the 17th century. The Basilians paired ascetic and contemplative life characteristic of orthodox monks with active missionary work and pastoral care that is typical of catholic monastic orders.

The Eastern Orthodox Church of the Holy Trinity rose on a hill in the civitas Ruthenica (Ruthenian city) in the eastern part of Vilnius back in the 14th century, but it is not known when the monastery was founded at this church. In 1514, in gratitude to God for the victory in the Battle of Orsha, Grand Hetman of Lithuania, Konstanty Ostrogski, built a brick Gothic church using a rectangular plan, and a monastery on the site. When the new Greek Catholic (Uniate) Church was established after the Union of Brest in 1596, this important hub of the Eastern Orthodox faith became a highly prominent centre of the new confession. The Order of St Basil the Great, or Basilians, became one of the key players in putting into practice the unity of the church. The Archimandrite of the Monastery of the Holy Trinity, and later, the Metropolitan of Kyiv, Joseph Benjamin Rutsky, fundamentally reformed monastic life in the Greek Catholic monasteries according to the model of Roman Catholic Religious Orders. His works were continued by the monk, Josaphat Kuntsevych, (he was martyred by the Eastern Orthodox believers in Polotsk in 1623 and was later officially acknowledged as the first martyred saint of the Greek Catholic Church). In 1617, the formerly autonomous communities of Uniate monks were united into the centralised Order of St Basil the Great, and the Basilian Province of the Holy Trinity was established, which was later divided into the Provinces of the Holy Trinity (Lithuania) and the Protection of the Mother of God (Poland) during the 18th century. The Basilians combined both the ascetic and contemplative characteristics of Eastern Orthodox monks with missionary and pastoral activity typical of Catholic Religious Orders. From 1628, a printing house operated at the Vilnius monastery, where Lithuanian publications were also printed. For some time after the partitions of the Polish-Lithuanian Commonwealth, the activity of Basilians remained unrestricted. However, in 1839, the church union was abolished and the Basilian monks and nuns of Vilnius formally converted to the Eastern Orthodox faith. In 1865, the Monastery of the Holy Trinity was officially closed. Later, with the change of regimes, the Church and the Monastery of the Holy Trinity changed hands, and in the Soviet period, the church was converted into a scientific laboratory. In 1994, the Basilians returned to their monastery.