St John's Archcathedral () is a Roman Catholic church within the Old Town precinct in Warsaw, Poland. The Brick Gothic structure stands on , adjacent to the Jesuit Church. St John's is one of three major cathedrals in the city, but it is the only temple that also possesses the title of an archcathedral. It is the mother church of the Archdiocese of Warsaw and one of Poland's national pantheons. Along with the old city, the church has been listed by UNESCO as a World Heritage Site.
