The Ambrosian Rite, also called the Milanese Rite, is a Catholic liturgical Western rite. The rite is named after Saint Ambrose, a bishop of Milan in the fourth century. The Ambrosian Rite, which differs from the Roman Rite, is used by some five million Catholics in the greater part of the Archdiocese of Milan, Italy (excluding, notably, the areas of Monza, Treviglio, Trezzo sull'Adda and a few other parishes), in some parishes of the Diocese of Como, Bergamo, Novara, Lodi and in about fifty parishes of the Diocese of Lugano, in the Canton Ticino, Switzerland.
Although at various points in its history the distinctive Ambrosian Rite has risked suppression, it survived and was reformed after the Second Vatican Council partly because Pope Paul VI belonged to the Ambrosian "rite", having previously been Archbishop of Milan. In the 20th century it also gained prominence and prestige from the attentions of two other scholarly Archbishops of Milan: Achille Ratti, later Pope Pius XI, and the Blessed Ildefonso Schuster, both of whom had been involved in studies and publications on the rite before their respective appointments.