Church of Immaculate Conception and Saint Nicholas in Oksa, Catholic church in Oksa, Poland

The Church of Immaculate Conception and Saint Nicholas in Oksa is a brick structure with a central floor plan and sparsely decorated interior spaces. A centrally placed pulpit defines the worship area, emphasizing the preaching tradition of its original Protestant design.

The Calvinist congregation was likely founded in the 1560s by Mikołaj Rej and completed in 1570 by his son Andrzej, who inherited Oksa in 1569. From the late 16th to the second half of the 17th century it was a main centre of Lesser Poland Calvinism, hosting numerous Protestant synods. In 1678 it passed to the Cistercians of Jędrzejów as a filial church of Konieczno. A major restoration in 1762–1763 added a new sacristy with the main altar, and in June 1914 Bishop Augustyn Łosiński consecrated it under St Nicholas.

From the late 16th century until the second half of the 17th century, the former Calvinist congregation in Oksa was one of the main centres of Lesser Poland Calvinism, and Protestant synods met there repeatedly. The Rej family, who founded the congregation, later built a new wooden church after the original passed to the Cistercians in 1678.

The church is accessible to visitors at coordinates 50.7262°N, 20.1076°E and continues to hold regular services. Access may be limited during worship hours, so it is best to plan a visit outside these times.

The church keeps a pulpit from its Calvinist period and 17th-century marble epitaphs of Andrzej Rej (d. 1601), Zygmunt Chomętowski (d. 1607) and Jan Czarniecki (d. 1658). These slabs were moved from the interior and set into the outer wall of the sacristy during the early 20th-century restoration. Mikołaj Rej, father of Polish literature, is probably buried here.