O'Beirne, Thomas Lewis (c.1747–1823), pamphleteer, polemicist, and bishop, was born at Farnagh, Co. Longford, son of Lewis O'Beirne, a Roman catholic farmer, and Margaret O'Beirne (née O'Meagher). Educated locally, and at Saint-Omer in Flanders, he and his brother were intended for the priesthood, but he left the Irish College in Paris without completing his studies. O'Beirne's early career is obscure, with rumours and allegations that he had been ordained a catholic priest, or conversely that he was a ‘mitred layman’, a protestant bishop who had never been consecrated a minister. It does appear that he was expelled from the Irish College for failings that led its president to decide that O'Beirne would make a terrible priest. Ambitious for advancement, O'Beirne converted to protestantism, studied at Trinity College, Cambridge, and became an anglican priest (1773). With the outbreak of the American war of independence he was appointed chaplain to the British fleet under Adm. Howe. When Howe was criticised for naval failures, O'Beirne rushed to his assistance in print with a pamphlet defending his reputation. It brought him to the attention of whig leaders in England, and marked the beginning of a long and successful career as a propagandist. In 1780 he wrote a comedy, ‘The generous impostor’, but it achieved little success. He also wrote two plays in collaboration with the duchess of Devonshire, but these added little to the reputation of either author.
When the duke of Portland (qv) was appointed lord lieutenant of Ireland in 1782 he appointed O'Beirne as his private secretary. Despite his conversion, O'Beirne remained tolerant of his old religion, and became its unlikely ally on a number of occasions. While in Dublin he suggested to Portland a state payment for the catholic clergy and consistently argued for this arrangement in the years ahead. The change of administration in 1783 ended his service, although Portland secured for him valuable preferments in Northumberland and Cumberland as compensation. A brief period of residence in France ended when he returned to England (1785) to write a pamphlet attacking Pitt's commercial propositions, and he played an important role in directing opposition to the proposals. He returned permanently to Ireland c.1791, and ministered at the rectory of Templemichael and the vicarage of Mohill in the diocese of Ardagh. It is believed that he served for a time in the same parish as his brother: one as the catholic priest, the other as the protestant minister. In 1795, when Earl Fitzwilliam (qv) became lord lieutenant of Ireland, Portland, now home secretary, recommended O'Beirne for the position of first chaplain. Appointed bishop of Ossory on 17 January, he was consecrated at Christ Church, Dublin, on 1 February. Again his service was brief. Fitzwilliam was recalled, and O'Beirne's hopes of advancement were temporarily dashed. However, he impressed many with his speech in the house of lords defending Fitzwilliam, and on 18 December 1798 he was appointed bishop of Meath. He supported a government veto on the appointment of catholic bishops, but showed no hostility to the question of catholic emancipation. On 29 January 1799 the countess of Granard commented that he was a ‘learned prelate whose irritable pride and low born self suffering makes him open to every attack which lowers his dignity’ (Scully, 22). Breaking with Portland, O'Beirne opposed the act of union (1800).
He died 17 February 1823 at his home at Ardbraccan House, Navan, Co. Meath. He married (1 November 1783) Jane Stuart; they had one son and two daughters. As a speaker he was ‘occasionally sublime, frequently pathetic, and always intelligible to his auditors’ (Gent. Mag., i (1822), 472).