The Diocese of Mantua is a Latin Church ecclesiastical territory or diocese of the Catholic Church in Italy. The diocese existed at the beginning of the 8th century, though the earliest attested bishop is Laiulfus (827). It has been a suffragan of the Archdiocese of Milan since 1819.

The Archdiocese of Milan is a Latin Church ecclesiastical territory or archdiocese of the Catholic Church in Italy which covers the areas of Milan, Monza, Lecco and Varese. It has long maintained its own Latin liturgical rite usage, the Ambrosian rite, which is still used in the greater part of the diocesan territory. Among its past archbishops, the better known are Ambrose, Charles Borromeo, Pope Pius XI and Pope Paul VI.