The Co-Cathedral Basilica of the Most Holy Trinity[1] (Polish: Bazylika Konkatedralna Trójcy Świętej) also called Chełmża Cathedral[2] is a religious building belonging to the Catholic Church located in the city of Chełmża, Poland.

[3][4] The church since 1994 has been the co-cathedral or alternate cathedral of the Diocese of Toruń (Dioecesis Thoruniensis or Diecezja Toruńska) and received the status of Minor Basilica in 1982.

Located on a lakeshore slope, it was built in stages from 1251 until the second quarter of the fourteenth century.

During the construction of the cathedral, the structure was twice destroyed (1267 and 1286) during Prussian invasions.

Reconstruction in the years 1968-1971 restored the church to its original appearance.