O'Sullivan, Samuel (1790–1851), Church of Ireland clergyman and writer, was born 13 September 1790 in Clonmel, Co. Tipperary, eldest son of John O'Sullivan, schoolmaster. His brother was the clergyman and writer Mortimer O'Sullivan (qv). Converting from catholicism to the Church of Ireland while still young, Samuel entered TCD (May 1812) and was made a scholar (1814). Like his brother, he was prominent in the College Historical Society and frequently won the society's debating medal. In 1816 he published a work of remarkable maturity, The agency of divine providence manifested in the principal transactions, religious and political, connected with the history of Great Britain from the reformation to the revolution in 1688 (Dublin, 1816). He entered holy orders and, graduating BA (1818), was ordained a priest by Charles Mongan Warburton (1755?–1826), bishop of Limerick (1806–20) and of Cloyne (1820–26), who was also a convert from catholicism. O'Sullivan later graduated MA (1825), BD, and DD (1837).
After his ordination, he was appointed curate of St Catherine's, Thomas St., Dublin (1818) and in 1819 became chaplain of the Marshalsea debtors' prison. In 1827 he was appointed chaplain to the Royal Hibernian Military School in the Phoenix Park, an office he held until his death. In the same year he became involved in the controversy regarding Fr Thomas Maguire (qv), and it was he who first referred to Maguire as ‘the sporting Fr Maguire’. He supported Lord John George Beresford (qv), archbishop of Armagh, in his opposition to the catholic relief bill of 1829, and also supported his stance on the tithe question.
O'Sullivan devoted much time to literary pursuits and, maintaining his link with TCD, contributed articles to the Dublin University Magazine from its foundation in 1833. Many of these were on historical subjects, especially the events of 1798, but he also wrote on matters such as the state of the Irish church and the Free Church movement in Scotland. The Young Irelander Charles Gavan Duffy (qv) claimed that many of these pieces displayed ‘furious bigotry’ and he accused O'Sullivan of infusing the Dublin University Magazine with a note of anti-catholic hysteria. O'Sullivan also published several articles in Fraser's Magazine and Blackwood's Magazine, and produced Catechism of the United Church of England and Ireland explained and confirmed (1850). In 1851 he was appointed Donnellan lecturer at TCD.
He died at the Royal Hibernian School, 6 August 1851, and was buried in the family plot in Chapelizod churchyard. He was survived by his wife (name unknown) and his son and daughter. In 1853 a collection of his unpublished articles was edited by his brother Mortimer and the Rev. J. C. Martin, and published in three volumes as Remains of the Rev. Samuel O'Sullivan.