The Ambrosian Rite is a Catholic Western liturgical rite, named after Saint Ambrose, a bishop of Milan in the fourth century, which differs from the Roman Rite. It is used by some five million Catholics in the greater part of the Archdiocese of Milan (excluding Monza, Treviglio and Trezzo sull'Adda), in some parishes of the Diocese of Como, Bergamo, Novara, Lodi, and in the Diocese of Lugano, Canton of Ticino, Switzerland.
The Ambrosian Rite has risked suppression at various points in its history. It was reformed after the Second Vatican Council (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 were involved in studies and publications on the rite.
History
The Church of Milan's own liturgy is named Ambrosian after its patron saint Ambrose. The Ambrosian Rite evolved and developed from the 4th century onwards. There is no direct evidence that the rite was the composition of St. Ambrose, but his name has been associated with it since the 8th century. It is possible that Ambrose, who succeeded the Arian bishop Auxentius of Milan, may have removed material seen as unorthodox by the mainstream church and issued corrected service books which included the principal characteristics distinguishing it from other rites.
According to St. Augustine (Confessiones, IX, vii) and Paulinus the Deacon (Vita S. Ambrosii, § 13), St. Ambrose introduced innovations, not indeed into the Mass, but into what would seem to be the Divine Office, at the time of his contest with the Empress Justina, for the Portian Basilica which she claimed for the Arians. St. Ambrose filled the church with Catholics and kept them there night and day until the peril was past. And he arranged Psalms and hymns for them to sing, as St. Augustine says, "after the manner of the Orientals, lest the people should languish in cheerless monotony"; and of this Paulinus the deacon says: "Now for the first time antiphons, hymns, and vigils began to be part of the observance of the Church in Milan, which devout observance lasts to our day not only in that church but in nearly every province of the West".
From the time of St. Ambrose, whose hymns are well-known and whose liturgical allusions may certainly be explained as referring to a rite which possessed the characteristics of that which is called by his name, until the period of Charlemagne (circ AD 800), there is a gap in the history of the Milanese Rite. However, St. Simplician, the successor of St. Ambrose, added much to the rite and St. Lazarus (438-451) introduced the three days of the litanies (Cantù, Milano e il suo territorio, I, 116). The Church of Milan underwent various vicissitudes and for a period of some eighty years (570-649), during the Lombard conquests, the see was moved to Genoa in Liguria.
In the eighth century, manuscript evidence begins. In a short treatise on the various cursus entitled "Ratio de Cursus qui fuerunt ex auctores" (sic in Cotton Manuscripts, Nero A. II, in the British Library), written about the middle of the eighth century, probably by an Irish monk in France, is found perhaps the earliest attribution of the Milan use to St. Ambrose, though it quotes the authority of St. Augustine, probably alluding to the passage already mentioned: "There is yet another Cursus which the blessed Bishop Augustine says that the blessed Ambrose composed because of the existence of a different use of the heretics, which previously used to be sung in Italy".