At the age of eighteen, Bartolomeo Cappellari joined the order of the Camaldolese[2] (part of the Benedictine monastic family) and entered the Monastery of San Michele in Murano, near Venice.

[3] He went to Rome in 1795 and in 1799 published a polemic against the Italian Jansenists titled II Trionfo della Santa Sede ("The Triumph of the Holy See"),[4][5] which passed through various editions in Italy and was translated into several European languages.

[6] When the army of the French Emperor Napoleon took Rome and arrested and deported Pius VII to France in 1809, Cappellari fled to Murano, where he taught in the Monastery of St. Michele of his Order, where he had first become a monk.

After Napoleon's final defeat, the Congress of Vienna re-established the sovereignty of the Papal States over central Italy and Cappellari was called back to Rome to assume the post of vicar general of the Camaldolese Order.

He was then appointed as Counsellor to the Inquisition, and later promoted to be Consultor (29 February 1820) and then, on 1 October 1826, Prefect of the Congregation of Propaganda Fide ("Propagation of the Faith"),[6] which dealt with all missionary work outside of the Spanish Empire, including missions to the non-Catholic states in Europe.

He publicly condemned the Polish revolutionaries, who he thought were seeking to undermine Russian Tsar Nicholas I's efforts to support the Catholic royalist cause in France by forcing him to divert his troops to suppress the uprising in Poland.

What finally drove the cardinals to make a decision was a message from the government of Parma notifying them that revolt was about to break out in the northern Papal States.

[12] In the course of the struggle that ensued, the Pope found it necessary more than once to call in Austrian troops to fight the red-shirted republicans engaged in a guerrilla campaign.

[14] The insurrections at Viterbo in 1836, in various parts of the Legations in 1840, at Ravenna in 1843 and at Rimini in 1845, were followed by wholesale executions and draconian sentences of hard labour and exile, but they did not bring the unrest within the Papal States under the control of the authorities.

Gregory XVI made great expenditures for defensive, architectural and engineering works, having a monument to Pope Leo XII built by Giuseppe Fabris in 1837.

Issued on 3 December 1839, as a result of a broad consultation among the College of Cardinals, the bull resoundingly denounced both the slave trade and the continuance of the institution of slavery.

During his reign, five saints were canonized (notably Alphonsus Liguori) and thirty-three Servants of God were declared Blessed (including the Augustinian Simon of Cascia).

In addition, many new religious orders were founded or supported and the devotion of the faithful to the Blessed Virgin Mary increased, both in private and public life.

According to Philippe Boutry, Alerame Maria Pallavicini (the Master of the Sacred Palace) was the in pectore cardinal announced on 24 November 1845; however, Pope Pius IX refused to publish his name upon his ascension to the papacy less than a year later.