The Church of the Assumption of the Blessed Virgin Mary in Kędzierzyn-Koźle is a historic monument dating back to 1751–1753. Built in the Baroque style, it serves as a filial church of the Parish of St. Sigismund and St. Hedwig of Silesia. Its architecture features a rectangular main nave, a distinct presbytery, and two sacristies. The church has plastered facades with decorative framing, a symmetrical front, and vaults adorned with beautiful polychrome paintings by Josef Anton Ernst Beyer from 1767, depicting a biblical scene with King Ahasuerus and Queen Esther. The interior is decorated with an 18th-century tabernacle featuring a sculpture of the Eucharistic Lamb and a painting of the Assumption of the Blessed Virgin Mary, created by an artist from Brabant in the 20th century. The church is also home to a 1935 Rieger organ with 17 stops.
Historically, the church has had a turbulent past, beginning with the establishment of a Franciscan monastery in 1431. It was later taken over by the Prussians in the 18th century and converted into an arsenal after secularization in 1810. In 1926, the parish purchased the church and, following renovations, began using it as a place of worship. It suffered significant damage twice—during World War II and the flood of 1997. The crypt contains the graves of German parish priests, adding to the site's historical significance. As a place of worship, the church stands as a witness to the changing fortunes of the region and the rich history of the local community.