O'Conor, Charles (1764–1828), priest, librarian, and antiquary, was born 15 March 1764 at Belanagare, Co. Roscommon, second of six sons of Denis O'Conor (d. 1804) and Catharine O'Conor (neé Browne), who also had six daughters. The O'Conors were catholic, descendants of a princely family in the west of Ireland; they had retained high social status, though in general without the financial security to underpin it. As second son, Charles was sent in 1779 to be educated for the priesthood at the Irish College, Rome, where he was ordained and was awarded the degree of DD. He was appointed to the parish of Castlerea or Kilkeevan (1789) by his kinsman, the O'Conor Don, but delayed his return, thus causing a breach with his father. He did not take up the living until 1791/2.
In 1796 he prepared for publication a memoir on the life and writings of his grandfather, the antiquarian Charles O'Conor (qv) (d. 1791), which highlighted the efforts made by O'Conor and other Irish catholics of substance to obtain the constitutional repeal of the penal laws. Denis O'Conor, who had had a leading role in the Catholic Committee, was alarmed by the possible consequences of such analysis in the contemporary political upheavals, and temporarily refused his son permission to study the works left to him by his grandfather. The author, taking counsel, rued his outspoken panegyric of his esteemed namesake and backed away from his own work. The first volume was suppressed as dangerous to the family; the manuscript of the second was burned by the author before reaching the printer. He destroyed what he thought was the whole run of the first volume and ten folios of the second, by casting them into a sewer, which communicated with the River Poddle. However, copies of the first volume survive in TCD and the BL.
Fr O'Conor had been reluctant to leave the libraries and magnificence of Rome to return to the poverty of the west of Ireland; in 1799 he was delighted when an opportunity of escape arose. George Grenville (qv), 1st marquess of Buckingham and former lord lieutenant, had long coveted the manuscripts and rare books amassed by Charles O'Conor senior. The O'Conor family at last agreed that they would allow the collection to go to Buckingham's palatial house at Stowe, and Charles O'Conor went with it, ostensibly to continue to study the historical materials. He was given permission by his bishop to leave his Castlerea parish, to become private chaplain to the marchioness of Buckingham, Mary Elizabeth Grenville, daughter of Robert Craggs Nugent (qv), Earl Nugent, a convert to the catholicism of her Irish ancestors. In 1799 he became librarian in Stowe, in charge of an impressive collection in an opulent gothicised setting.
O'Conor published (1818–19) Bibliotheca MSS Stowensis, a two-volume catalogue of the Stowe library manuscripts, including those purchased by Buckingham from the O'Conors. They included the Annals of Ulster, of Inisfallen, of Boyle, and of Tigernach, and the only original then known of the first part of the Annals of the Four Masters. At the same time as working on the catalogue, he published four volumes of Rerum Hibernicarum scriptores veteres (1814–28), of which 200 copies were printed at the huge expense of £3,000, met by the marquess of Buckingham. A previously unknown fifth volume, containing the cancelled pages from the first four volumes, was acquired by the NLI in 1956. In this ambitious and costly work, O'Conor drew attention to the existence of early Irish documents, compared versions of Irish manuscripts between Stowe and other libraries, provided translations into Latin, and published the first facsimiles of some. O'Conor's linguistic and historical abilities were not equal to his grandfather's, and certainly not commensurate with the importance of his material. More expert scholars have wholeheartedly condemned his efforts. John O'Donovan (qv) asserted that O'Conor's scholarship and transcriptions were faulty; T. J. Westropp (qv) noted that O'Conor revived the moribund theory that round towers were built to house hermits and penitents. O'Conor's approach to Irish history, and his evident veneration of the glories of the British constitution, the patronage of English aristocrats, and the magnificence of Stowe, left him open to criticism at a time when Irish national identity was being reforged in the aftermath of the union of parliaments in 1801; J. J. Kelly (1882), for instance, criticised him for discrediting the work of his grandfather and for writing from an Anglo-Irish viewpoint. However, the connection with Buckingham and with his grandfather's illustrious name undoubtedly boosted the prestige of the subject-matter when most of his contemporaries had little enough interest in early Irish history, and O'Conor was something of a pioneer in Irish studies.
Those same connections might well have given O'Conor real importance in the history of his country or of his religion. As a catholic priest in the Buckingham household, a trusted intimate of the family, he might have been able through his social contacts to influence English public opinion and even events; contemporary opponents of catholicism in England certainly feared the possible adverse effects. However, the catholic hierarchy was to be deeply disappointed in O'Conor; he displayed an unflattering reluctance to join them as a bishop, on four occasions between 1803 and 1810 when family connections seemed to be pushing him towards the bishoprics of Achonry and Elphin. Even worse, some of his writings were so objectionable to the church authorities that in 1810 Archbishop John Thomas Troy (qv) told the O'Conor Don that he would not support his own brother for a bishopric if that brother had written Columbanus ad Hibernos. O'Conor wrote seven lengthy pamphlets, all bearing this title, between 1810 and 1813. The fifth Columbanus address (1812) was dedicated to the marquess of Buckingham. Only the first, over the pseudonym ‘Columbanus’, was even somewhat anonymous; the opinions expressed were so repugnant to the Irish hierarchy and prominent lay catholics (including his own family) that a later commentator (W. J. Fitzpatrick, Irish wits and worthies (1876), 295, cited by James Sack) thought that O'Conor must have been mad when he wrote them.
The pamphlets particularly concerned the then highly contentious issue of the appointment of catholic bishops; O'Conor's views were coloured by a Gallican distrust of the papacy and he strongly supported the right of the government to veto any appointments it found unacceptable. Long asides on seventeenth-century history, the ‘ridiculous miracles’ of Irish saints’ lives, and the overweening merits of the English constitution, further enraged the church authorities and his compatriots (quoted by Sack, 137); he was regarded as almost an apostate. In June 1812 the vicar general of London barred O'Conor from exercising his priestly functions, and he was apparently also barred from the sacraments, though he afterwards disputed this; when he visited Ireland in 1812, Archbishop Troy likewise forbade him to say mass in public or private. O'Conor's protests and assertions of persecution were incessant but unavailing for twelve years; he threatened to ignore the suspension, and even appealed to the pope for redress, unsuccessfully in 1815 and 1818. The papal authorities understandably declined to intervene; finally in 1824 Bishop Poynter reinstated him.
By then, O'Conor seems to have developed mental problems; by 1827 he was suffering from the delusion that he was deliberately being starved by order of the marquess of Buckingham. O'Conor left Stowe on 4 July 1827. The Nation (26 March 1853) claimed that O'Conor was thereafter a patient at Dr Harty's asylum in Finglas, Dublin, apparently along with John Lanigan (qv), whom he would have known in the Irish College. His family twice unavailingly demanded that the paper's editor should issue a correction. The old priest died 29 July 1828 in his family's house at Belanagare, and he was buried in Ballintober abbey.
His brother Owen became the O'Conor Don in 1820. His younger brother Matthew (d. 1844), who left the seminary in Rome to become a barrister, wrote a History of Irish catholics from the settlement in 1691 (1813), Military history of the Irish nation (1845), and other works. A bibliography of Charles O'Conor's works is in Douglas Hyde (qv) and D. J. O'Donoghue, Catalogue of the books and manuscripts comprising the library of the late Sir John Gilbert (1918), 593–4.