A Papal Mass is the Solemn Pontifical High Mass

Pontifical High Mass

In the context of the Tridentine Mass of the Roman Catholic Church, a Pontifical High Mass, also called Solemn Pontifical Mass, is a Solemn or High Mass celebrated by a bishop using certain prescribed ceremonies. The term is also used among Anglo-Catholic Anglicans.-Origins:In the early Church,...

 when offered by the Pope

Pope

The Pope is the Bishop of Rome, a position that makes him the leader of the worldwide Catholic Church . In the Catholic Church, the Pope is regarded as the successor of Saint Peter, the Apostle...

 of the Roman Catholic Church

Roman Catholic Church

The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

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There are numerous special ceremonials which are particular to the pope. A Solemn Papal Mass would be celebrated on solemn occasions such as a Papal Coronation

Papal Coronation

A papal coronation was the ceremony of the placing of the Papal Tiara on a newly elected pope. The first recorded papal coronation was that of Pope Celestine II in 1143. Soon after his coronation in 1963, Pope Paul VI abandoned the practice of wearing the tiara. His successors have chosen not to...

, an ex cathedra

Ex Cathedra

Ex Cathedra is a British choir and early music ensemble based in Birmingham in the West Midlands, England. It performs choral music spanning the 15th to 21st centuries, and regularly commissions new works....

pronouncement, the canonization

Canonization

Canonization is the act by which a Christian church declares a deceased person to be a saint, upon which declaration the person is included in the canon, or list, of recognized saints. Originally, individuals were recognized as saints without any formal process...

 of a saint

Saint

A saint is a holy person. In various religions, saints are people who are believed to have exceptional holiness.In Christian usage, "saint" refers to any believer who is "in Christ", and in whom Christ dwells, whether in heaven or in earth...

, or a major feast such as Easter

Easter

Easter is the central feast in the Christian liturgical year. According to the Canonical gospels, Jesus rose from the dead on the third day after his crucifixion. His resurrection is celebrated on Easter Day or Easter Sunday...

 or Christmas

Christmas

Christmas or Christmas Day is an annual holiday generally celebrated on December 25 by billions of people around the world. It is a Christian feast that commemorates the birth of Jesus Christ, liturgically closing the Advent season and initiating the season of Christmastide, which lasts twelve days...

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Many of the ceremonies that were once connected with such a Mass have fallen out of use since the time of Pope Paul VI

Pope Paul VI

Paul VI , born Giovanni Battista Enrico Antonio Maria Montini , reigned as Pope of the Catholic Church from 21 June 1963 until his death on 6 August 1978. Succeeding Pope John XXIII, who had convened the Second Vatican Council, he decided to continue it...

 and some, such as the reservation of Communion to the Pope, the deacon and the subdeacon, since the time of Pope Pius X

Pope Pius X

Pope Saint Pius X , born Giuseppe Melchiorre Sarto, was the 257th Pope of the Catholic Church, serving from 1903 to 1914. He was the first pope since Pope Pius V to be canonized. Pius X rejected modernist interpretations of Catholic doctrine, promoting traditional devotional practices and orthodox...

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What follows is a description of usage in the early twentieth century, before the liturgical reforms of Pope Paul VI.
In the papal Mass a cardinal-bishop acted as assistant priest; this honor fell on the most solemn occasions to the Cardinal-bishop of Ostia, the Dean of the College of Cardinals

Dean of the College of Cardinals

The Dean of the Sacred College of Cardinals is the president of the College of Cardinals in the Roman Catholic Church, and as such always holds the rank of Cardinal Bishop. The Dean is not necessarily the longest-serving member of the whole College...

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