The Roman Catholic parish in Olesko, 72 kilometres from Lviv, has a long history of over five hundred years. For a long time, 1481 was taken as the date of its foundation, but more recent literature points to a date more than fifty years earlier - 1428.

No news of the original parish church in Olesko has survived, although we suspect that it was a wooden structure. The first recorded consecration of the Olesko church was in 1597, when it was consecrated by Bernard Maciejowski, Bishop of Lutsk. However, the date of the beginning of the temple's construction remains unknown to us. Transfers from the 17th century claimed that Jadwiga Kamieniecka was the founder of the church.

The parish church in Olesko, despite being located in the Ruthenian voivodship, belonged for three hundred years to the Diocese of Luck. The parish was not annexed to the Lvov Archdiocese until after the Partitions of Poland, by order of Emperor Joseph II.

In the 19th century, the church was destroyed by fires twice. The first of these broke out in 1806, and after the departure of the parish priest, the parish was run by the local Capuchins from 1808 to 1809. The second of the fires broke out in 1841. After it, the Olesko church was extensively rebuilt. The temple was divided into three naves, and new vaults and roofs were added.

20th century
In 1927 the church was thoroughly rebuilt by the architect Bronisław Wiktor - the annexes were given new covers, a new gable was made, the stone frieze on the body and the presbytery was partly turned over, the signature tower was replaced, and a new wall was erected in the fence. The architecture of the church to this day has largely retained the state of this particular reconstruction. A few years later, between 1929 and 1934, the pulpits, altars and organ were renovated.

After the Second World War, the church was closed. From then on, it was used as a warehouse, which left its mark on the state of preservation of the church; only the takeover of the church by the Lviv Picture Gallery stopped the process of devastation of the building. After forty years of non-existence, the Olesko parish was re-registered in 1991. However, the Holy Trinity Church could not be recovered. Two years later, in 1993, the Holy Trinity Church in Olesko was handed over to the Ukrainian Autocephalous Orthodox Church.

Architecture:
Located on the eastern side of the market square, the Holy Trinity Church in Olesko was built mainly of brick; however, stone was used in the ground floor and in architectural details. It consists of a three-bay and three-nave (due to the reconstruction of the 1840s, originally the body of the church was single-nave) hall-type body covered with a barrel and cross vault and a two-bay presbytery closed trilaterally with a cross-ribbed vault.

The body of the church is separated from the main body by two chapels. The chapel of the Immaculate Conception of Mary to the north and the chapel of St John the Evangelist to the south are located on the south side. To the south is the Chapel of St John the Evangelist, which is also the lower storey of the bell tower. At the front, the church has a square-shaped annex with a porch and a choir. In the eastern part of the church we can also find the Danilovichs' burial crypt.

Although the Holy Trinity Church in Olesko was built in the second half of the 16th century, several elements of its architecture - the plan of the body and chancel, the cross-ribbed vault in the chancel and the corner buttresses - betray the inspiration of Gothic sacral architecture. On the other hand, the semi-circular window closures and the architectural decoration (especially the portals framing the entrances from the porch to the nave and from the presbytery to the sacristy) are all reminiscent of the late Renaissance.

The roofs of the Olesko church are mostly pitched; only the apse has a multi-pitched roof and the sacristy has a pent roof. All the roofs, as well as the dome of the chapel and the helmet of the tower, are covered with sheet metal.

Church equipment
The equipment of the Olesko church consists of a Rococo main altar, four side altars and pulpits. They were made in the third quarter of the 18th century in wood. In the church we also find the epitaph of Jan Danilovich, who died in 1618, made of red marble, decorated with an oval medallion depicting a boy as a knight. In the floor in front of the entrance to the crypt, we can also find the tombstone of Jan Danilovich, Voivode of Rus, who died in 1628, which is decorated with four coats of arms.

Some of the furnishings have been preserved in the church, but the fate of many items, especially the equipment in the sacristy, remains unknown to this day.