Slattery, Michael (1783–1857), catholic archbishop of Cashel and Emly, was born in Tipperary town, son of Thomas Slattery, landed gentleman. Although a Roman Catholic, he attended the local Church of Ireland school and in 1799 entered TCD to study law. He graduated BA (1804) and later MA (1832) but abandoned his legal studies to begin training for the catholic priesthood. In September 1805 he entered the seminary in Carlow, and in 1809 was ordained as a priest of the Cashel archdiocese, being appointed professor of philosophy at Carlow after his ordination. He later served as PP of Solohead (1815–17) and Borrisoleigh (1817–33). His superiors soon realised that he was a highly intelligent and forceful character. He stamped out faction-fighting in the parishes under his control and also collected enough funds to build a new church at Ileagh. James Warren Doyle (qv), bishop of Kildare and Leighlin, took an active interest in his career and, when the see of Cashel fell vacant in 1822, proposed that Slattery be appointed as the next archbishop. Although this attempt to secure him a bishopric failed, he retained the patronage of influential members of the catholic hierarchy. In June 1833 he became president of Maynooth College but only held the appointment for a few months, being appointed archbishop of Cashel in December 1833. He resigned from the presidency of Maynooth in January 1834, and was consecrated as archbishop on 24 February. His immediate priority was to raise enough funds to complete St Patrick's College, Thurles, which opened in September 1837. He also tried to remedy the lax discipline among his clergy and was deeply hostile to any threats to his privileges as a bishop, resisting government attempts to control the appointment of workhouse chaplains.
In 1845 he gained prominence as one of the most vocal opponents of Sir Robert Peel's (qv) proposals for the establishment of the queen's colleges. In cooperation with John MacHale (qv), archbishop of Tuam, he led the opposition to the proposed ‘godless colleges’ at Cork, Galway, and Belfast, denouncing William Crolly (qv), archbishop of Armagh, and Daniel Murray (qv), archbishop of Dublin, who supported them. He engaged in a long correspondence with the authorities in Rome, dealing mainly with Paul Cullen (qv), rector of the Irish College. Ultimately the matter was settled, from the church's viewpoint, with Cardinal Fransoni's condemnation of the queen's colleges in October 1847. Ireland was by that stage in the grip of the famine, and the Vatican decree went largely unnoticed by both the government and the Irish population.
Slattery was a bishop cast very much in the ultramontane mould and, appointed as the metropolitan of Munster, tried to instil in his clergy an understanding of Rome's complete authority, forbidding priests from engaging in political controversy. In the months preceding the Young Ireland rebellion of 1848, there was an outbreak of anti-clericalism in his diocese, several priests actually being attacked. Fearing the onslaught of a movement calling for greater secularisation, he castigated the leaders and philosophy of Young Ireland in a series of scathing sermons. With Archbishop MacHale, he was largely instrumental in securing the archdiocese of Armagh for Paul Cullen in 1850 and gave him continued support in later years. In 1850 he organised a synod at Thurles, the first national synod to be held in Ireland since 1177. A member of the Catholic University committee since 1850, Slattery was an enthusiastic fund-raiser for the project, though he did not attend many meetings of the committee ; he was increasingly ill from 1852. When John Henry Newman (qv) visited Thurles in 1850, and subsequently, he dealt with Slattery's vicar general and successor, Patrick Leahy (qv).
Until the end of his career, Slattery continued to resist government efforts to encroach on church privilege, leading the opposition to the Nuns' Property Disposal Bill (1854), and the Bill to Facilitate the Recovery of Personal Liberty in Certain Cases (1855). The latter was introduced as a result of allegations that young women were being detained against their will in convents. Slattery opposed it not only because he found the allegations obnoxious, but because he disputed the right of investigators to enter convents. Taking an interest in all aspects of his parishioners' lives, in 1854 he ordered his priests to conduct a survey of labourers' wages and diet which collected a wealth of information.
Slattery has been largely overlooked by church historians in Ireland, but throughout his career he proved himself a churchman of ability: he constantly upheld the authority of the curia, opposed government attempts to interfere in church matters, and tried to curb Gallican and radical political tendencies among his clergy. There is a large collection of Slattery's papers in the Cashel diocesan archive in Thurles. Further collections of his letters are held in the Cullen papers in the Dublin diocesan archive and in the Newman papers in the Oratory of St Philip Neri in Birmingham. He died on 4 February 1857 and was buried in Thurles chapel, the site of the later cathedral.