(2 Feb. 1831–1 June 1846)
Born at Belluno, Venetia, on 18 Sept. 1765, son of an aristocratic lawyer, Bartolomeo Alberto Cappellari entered at 18 the Camaldolese (i.e. strict Benedictine) monastery of S. Michele at Murano, Venice, against the wishes of his parents, taking the name Mauro, and after ordination in 1787 became (1790) professor of science and philosophy. Coming to Rome in 1795 as assistant to the procurator general of his order, he published in 1799, during Pius VI's imprisonment by the French Directory, The Triumph of the Holy See and the Church against the Attacks of Innovators, upholding papal infallibility and the temporal sovereignty of the holy see, and denouncing all claims to subject it to state control. He was summoned back to Rome in 1800 by Pius VII and in 1805 made abbot of S. Gregorio in Monte Celio, and in 1807 procurator general of the Camaldolese order. Forced to leave Rome after Pius VII's arrest by Napoleon, he taught at Murano and Padua, but returned in 1814. After being consultant to several congregations and examiner of prospective bishops, he was named vicar-general of the Camaldolese in 1823, and cardinal in 1825—though the fact was not published until the following year. As prefect of the Propaganda (1826) he gave a new impulse to missionary enterprise; he also assisted Leo XII and Pius VIII in important business. At the difficult, 50-day conclave of 1830 he was eventually elected with the backing of the zelanti and of the Austrian statesman Klemens von Metternich (1773–1859), who wanted an absolutist-minded pope who would not give way to ‘the political madness of the age’.
An austere, learned monk, hostile to modern trends (he banned railways in his domains, calling them ‘chemins d'enfer’) and to Italian nationalism in particular, Gregory was immediately faced with uprisings in the papal states and in Rome itself, and with calls for a federal republic. At first he attempted to deal with the restless population himself, and sent a cardinal legate, but after the arrest of the legate he had to seek military aid from Austria, which quickly crushed the revolts. The great powers then intervened (31 May 1831), demanding radical administrative, judicial, and constitutional reforms in the states. Gregory was prepared to concede limited changes, but not to grant elected assemblies or a council of state composed of laymen. As a result disorders broke out afresh, Austrian troops had to be recalled, France seized Ancona, and for seven years the papal states were under military occupation. Supported by reactionary secretaries of state, T. Bernetti and (from 1836) L. Lambruschini, Gregory had to deal with mounting discontent and simmering rebellion for his entire reign, while the cost of maintaining a repressive regime with hired soldiers drained his treasury.
Gregory was equally uncompromising in the realm of ideas, and in his encyclical Mirari vos (15 Aug. 1832) denounced the notions of freedom of conscience and of the press, and of separation of church and state, associated with F. R. de Lamennais (1782–1854), the champion of Catholic liberalism, and his newspaper L'Avenir. Although he had received Lamennais kindly in Nov. 1831, he condemned his reply to Mirari vos in June 1834, and then condemned Lammenais's Words of a Believer, published in April 1834, in an encyclical, Singulari nos, published in July. Convinced that modern liberalism had its roots in indifferentism, he branded this intellectual attitude, as well as the activities of the London Bible Society and the New York Christian Alliance, in Inter praecipuas machinationes (8 May 1844). Among other teachings he censured were (26 Sept. 1835) the rationalism of Georg Hermes (1775–1831) and the fideism of the abbé L. E. M. Bautain (1796–1867), who placed an excessive emphasis on faith. In the political field he stood for the independence of the church and had a horror of revolution, and his reign was a continuous struggle in the service of conservative ideals. For years he was at odds with Portugal and Spain, whose governments were embarking on unacceptable anticlerical legislation, and with Switzerland, where the Articles of Baden (21 Jan. 1834) sought to eliminate papal authority over Swiss Catholics. He protested (1845) with some success against Nicholas I's persecution of Catholics in Russia, but when the Poles revolted against the tsar in 1830–31, he addressed an encyclical (9 June 1832) to their bishops condemning revolutionary movements. The same respect for constituted authority led him, in a private letter from the Propaganda (15 Oct. 1844), to discourage the Irish clergy from political action. Yet he could on occasion be accommodating, permitting the collaboration of Catholics with liberals in the creation of Belgium, and in response to government pressure acquiesced in the temporary withdrawal of the Jesuits from France in 1845. In Prussia, which insisted that children of mixed marriages should follow their father's religion, he took a strong line, recalling (27 Mar. 1832 and 12 Sept. 1834) Pius VIII's ruling and protesting (12 Dec. 1837) against the imprisonment of an archbishop who had followed it. With the accession of Frederick William IV (June 1840), however, his diplomacy was able to reach an advantageous arrangement (1841) under which Prussia gave up the right to interfere in mixed marriages; in addition the freedom of episcopal elections was guaranteed and a special department for Catholic affairs was set up in the ministry of religion.