Basilica of St. John the Evangelist, Oleśnica

The Basilica of St. John the Evangelist (Polish: Bazylika Świętego Jana Apostoła), formerly the Castle Church (German: Schlosskirche), is a Roman Catholic parish church in the Oleśnica West deanery within the Archdiocese of Wrocław. Between 1538 and 1945, the building functioned as a Protestant church dedicated to John the Baptist. On 8 October 1998, it received the honorary title of minor basilica.

Documentary evidence of the church and its parish first appears in records dating to 1230. The brick structure was constructed in the second half of the 13th century and served as the castle church. The building underwent repeated reconstructions by the Poděbrady, Württemberg, and Hohenzollern families.

These modifications have resulted in an architectural form that integrates elements of Gothic, Renaissance, Mannerism, and Baroque styles. In 1616, a passage was added, connecting the church to the Oleśnica Castle. An enlargement project undertaken in 1905 culminated in a structural collapse of the southern nave and the main nave. In 1910, the church was subsequently rebuilt and modernized.

The interior contains monuments such as the only surviving chained library in Central Europe.