Promulgation of reformed and codified Missale Romanum (Roman Missal)
Papal Bull of Pope St. Pius V
July 14, 1570
Servant of the Servants of God
For An Everlasting Memory
From the very first, upon Our elevation to the chief Apostleship, We gladly turned our mind and energies and directed all out thoughts to those matters which concerned the preservation of a pure liturgy, and We strove with God's help, by every means in our power, to accomplish this purpose. For, besides other decrees of the sacred Council of Trent, there were stipulations for Us to revise and re-edit the sacred books: the Catechism, the Missal and the Breviary. With the Catechism published for the instruction of the faithful, by God's help, and the Breviary thoroughly revised for the worthy praise of God, in order that the Missal and Breviary may be in perfect harmony, as fitting and proper—for its most becoming that there be in the Church only one appropriate manner of reciting the Psalms and only one rite for the celebration of Mass—We deemed it necessary to give our immediate attention to what still remained to be done, viz, the re-editing of the Missal as soon as possible.
Hence, We decided to entrust this work to learned men of our selection. They very carefully collated all their work with the ancient codices in Our Vatican Library and with reliable, preserved or emended codices from elsewhere. Besides this, these men consulted the works of ancient and approved authors concerning the same sacred rites; and thus they have restored the Missal itself to the original form and rite of the holy Fathers. When this work has been gone over numerous times and further emended, after serious study and reflection, We commanded that the finished product be printed and published as soon as possible, so that all might enjoy the fruits of this labor; and thus, priests would know which prayers to use and which rites and ceremonies they were required to observe from now on in the celebration of Masses.
Let all everywhere adopt and observe what has been handed down by the Holy Roman Church, the Mother and Teacher of the other churches, and let Masses not be sung or read according to any other formula than that of this Missal published by Us. This ordinance applies henceforth, now, and forever, throughout all the provinces of the Christian world, to all patriarchs, cathedral churches, collegiate and parish churches, be they secular or religious, both of men and of women—even of military orders—and of churches or chapels without a specific congregation in which conventual Masses are sung aloud in choir or read privately in accord with the rites and customs of the Roman Church. This Missal is to be used by all churches, even by those which in their authorization are made exempt, whether by Apostolic indult, custom, or privilege, or even if by oath or official confirmation of the Holy See, or have their rights and faculties guaranteed to them by any other manner whatsoever.
This new rite alone is to be used unless approval of the practice of saying Mass differently was given at the very time of the institution and confirmation of the church by Apostolic See at least 200 years ago, or unless there has prevailed a custom of a similar kind which has been continuously followed for a period of not less than 200 years, in which most cases We in no wise rescind their above-mentioned prerogative or custom. However, if this Missal, which we have seen fit to publish, be more agreeable to these latter, We grant them permission to celebrate Mass according to its rite, provided they have the consent of their bishop or prelate or of their whole Chapter, everything else to the contrary notwithstanding.
All other of the churches referred to above, however, are hereby denied the use of other missals, which are to be discontinued entirely and absolutely; whereas, by this present Constitution, which will be valid henceforth, now, and forever, We order and enjoin that nothing must be added to Our recently published Missal, nothing omitted from it, nor anything whatsoever be changed within it under the penalty of Our displeasure.
We specifically command each and every patriarch, administrator, and all other persons or whatever ecclesiastical dignity they may be, be they even cardinals of the Holy Roman Church, or possessed of any other rank or pre-eminence, and We order them in virtue of holy obedience to chant or to read the Mass according to the rite and manner and norm herewith laid down by Us and, hereafter, to discontinue and completely discard all other rubrics and rites of other missals, however ancient, which they have customarily followed; and they must not in celebrating Mass presume to introduce any ceremonies or recite any prayers other than those contained in this Missal.
Furthermore, by these presents [this law], in virtue of Our Apostolic authority, We grant and concede in perpetuity that, for the chanting or reading of the Mass in any church whatsoever, this Missal is hereafter to be followed absolutely, without any scruple of conscience or fear of incurring any penalty, judgment, or censure, and may freely and lawfully be used. Nor are superiors, administrators, canons, chaplains, and other secular priests, or religious, of whatever title designated, obliged to celebrate the Mass otherwise than as enjoined by Us. We likewise declare and ordain that no one whosoever is forced or coerced to alter this Missal, and that this present document cannot be revoked or modified, but remain always valid and retain its full force notwithstanding the previous constitutions and decrees of the Holy See, as well as any general or special constitutions or edicts of provincial or synodal councils, and notwithstanding the practice and custom of the aforesaid churches, established by long and immemorial prescription—except, however, if more than two hundred years' standing.
It is Our will, therefore, and by the same authority, We decree that, after We publish this constitution and the edition of the Missal, the priests of the Roman Curia are, after thirty days, obliged to chant or read the Mass according to it; all others south of the Alps, after three months; and those beyond the Alps either within six months or whenever the Missal is available for sale. Wherefore, in order that the Missal be preserved incorrupt throughout the whole world and kept free of flaws and errors, the penalty for nonobservance for printers, whether mediately or immediately subject to Our dominion, and that of the Holy Roman Church, will be the forfeiting of their books and a fine of one hundred gold ducats, payable ipso facto to the Apostolic Treasury. Further, as for those located in other parts of the world, the penalty is excommunication latae sententiae, and such other penalties as may in Our judgment be imposed; and We decree by this law that they must not dare or presume either to print or to publish or to sell, or in any way to accept books of this nature without Our approval and consent, or without the express consent of the Apostolic Commissaries of those places, who will be appointed by Us. Said printer must receive a standard Missal and agree faithfully with it and in no wise vary from the Roman Missal of the large type.
Accordingly, since it would be difficult for this present pronouncement to be sent to all parts of the Christian world and simultaneously come to light everywhere, We direct that it be, as usual, posted and published at the doors of the Basilica of the Prince of the Apostles, also at the Apostolic Chancery, and on the street at Campo Flora; furthermore, We direct that printed copies of this same edict signed by a notary public and made official by an ecclesiastical dignitary possess the same indubitable validity everywhere and in every nation, as if Our manuscript were shown there. Therefore, no one whosoever is permitted to alter this notice of Our permission, statute, ordinance, command, precept, grant, indult, declaration, will, decree, and prohibition. Should know that he will incur the wrath of Almighty God and of the Blessed Apostles Peter and Paul.
Given at St. Peter's in the year of the Lord's Incarnation, 1570, on the 14th of July of the Fifth year of Our Pontificate.
In the Year of the Birth of our Lord 1570, the thirteenth indiction, on the nineteenth day in the month of July. The most holy bishop in Christ, and by Divine Providence our Father and Lord Pope, Pius V, in his fifth year, published this letter of rescript and had it affixed to the doors of the Basilica of the Prince of the Apostles, at the Apostolic Chancery, and the front of the Campo Flora, as is customary, for us by the Couriers Ioannem Andream Roerium and Phiilbertum Cappuis.
Scipio de Octavianis, Magister Cursorum
 This is the Latinized name of Cesar Grolier who was a Secretary of Latin Briefs to three popes.
 Again, the Latinized name of H. Cumyn, obviously a papal secretary (or perhaps a notary), though his full identity has been lost.
 An indiction (Indictione in Latin) is a chronological term referring to a system of dating events within a fiscal period of fifteen years. It was established by the Roman Emperor Constantine in 313 and continued to be used by the papal court at least into the 16th century.
 That is, “Master Courier” or papal messenger, known today in Italian as Maestro Generale delle Poste Pontificie, or the “Master General of the Pontifical Post (Post Office).”
Explanatory extract from J.B. O'Connell
The Celebration of Mass: A Study of the Rubrics of the Roman Missal (Bruce, 1964)
The Missal of Pius V (1570)
7. The Council of Trent (1545-63) decided that a revision of the liturgical books was necessary—owing to the diversity of usage which had arisen and to the influence of Protestantism on the Liturgy—and set up a commission for that purpose in 1562. When the Council ended, the work of revision was entrusted to the Pope, Pius IV (1559-65), and to his successor, S. Pius V (1566-72). On July 14, 1570, the revised Missal was published, and imposed, by the bull Quo primum tempore, on all churches of the West that could not claim to have had legitimately in use for more than two centuries another Missal. This Missal of Pius V was the first Missal to be officially published by the Holy See.
8. The new Missal did not introduce a new rite. Its compilation was a reform, and consisted in the codification of the traditional rubrics, in the correction of texts, and in securing agreement between the Missal and the newly reformed Roman Breviary (approved in 1568). It definitely fixed the text of the Ordinary—introducing officially into it the preparatory prayers, the Offertory prayers, the prayers preceding and following Communion, the Blessing and the Gospel of St. John—and greatly reduced the number of Sequences, of Prefaces, and of proper Communicantes and Hanc igitur.
9. The Latin text in the Pianine Missal is the Itala Vetus for the sung texts of the Proper (i.e., Introit, Gradual, Tract, Alleluia, Offertory and Communion verses); the Vulgate for the readings (lesson, Epistle, Gospel).
 This bull still appears at the beginning of every Missal.
 Taking advantage of this exception the churches of Milan, Toledo, Braga, Lyon, Bayeux, and the Canons Regular of Premontré, and the Calced Carmelites, the Carthusians, and the Dominicans have kept their own Missal.
 To four; a fifth—Stabat Mater—was added later on.
 To eleven; four have since been added.
 To six and two.
 The Old Latin version (dating from the second century), in use before the Vulgate was made.
 The version of the New Testament published by S. Jerome about 382 (a revision of the Itala Vetus).
"Bulla" refers to the round seal. This one is of Leo XIII.