St. John Cantius Church is a historic church of the Roman Catholic Archdiocese of Chicago located in Chicago, Illinois. It is a prime example of the so-called 'Polish Cathedral style' of churches in both its opulence and grand scale. Along with such monumental religious edifices as St. Mary of the Angels, St. Hedwig's or St. Wenceslaus, it is one of the many Polish churches that dominate over the Kennedy Expressway.
St. John Cantius church has witnessed a number of famous visitors within its walls. In March 1989, the parish hosted a visit by Tadeusz Mazowiecki, Prime Minister of the newly-democratic Poland, while in 1998, Józef Glemp, the Cardinal Primate of Poland came to celebrate a Mass of Thanksgiving and bless the church's new copper cupola.