Fitzgerald, John Fraunceis (1791–1854), hereditary knight of Glin and scholar, was born 28 June 1791, only son of John Bateman Fitzgerald (1756–1803), knight of Glin and colonel of Limerick volunteers, and Margaretta Maria Fitzgerald (née Gwyn; d. 1801) of Combe Florey, Somerset, England. Fostered, as was customary, to the Costelloe family of Killeany, parish of Glin, he attended a classical school in the village before boarding at Winchester College (1802–8) and attending Christ's College, Cambridge (1809–12), graduating with a BA and MA. He was enabled at the close of his minority to take the first steps towards restoring the estate, mortgaged since 1793, to solvency. In 1813 he recovered legal possession from the major creditor and settled outstanding encumbrances by the sale of almost half of the property (12,000 acres in 1800). He was not tempted to exact increased rents in the parish, however, and indeed abated charges in 1816 and 1822. Being an only child and therefore relieved of the necessity to provide for dependent siblings, he made free use of estate income to renovate Glin House and demesne in the early 1820s and reorder the street layout of Glin village.
Made JP and DL in 1814, on his return to the estate, he took part diligently in county business, adjudicating summarily in petty cases in the parish, and intermittently exerting himself in more serious agrarian and homicide cases. When the body of Ellen Hanley (qv) (known later as ‘the Colleen bawn’) was washed up at Moneypoint, Co. Clare, in September 1819, he was one of three magistrates to hold an inquest into her death, signing a verdict of wilful murder against a local gentleman. He later posted a description of the accused to Dublin Castle, thus going against the reluctance of county gentry to intervene against a member of their own class. He may have been particularly sensitive to the brutal abuse of trust committed against a peasant mistress by a landed gentleman, having a reputation himself for sexual indiscretions with peasant women in Glin. Nicknamed ridire na mban (the knight of the women), he apparently kept a succession of mistresses in a lodge at the edge of the demesne between the 1820s and the 1850s, weathering the ire of the Rev. Daniel O'Sullivan, the catholic parish priest from 1815 to 1842, who composed wrathful satirical verse in Irish on the subject. Attempted social exclusion within the parish, and later the threatened excommunication of one of his mistresses, Mary Wright (d. 1833) for public scandal, prompted the knight to haul the priest before a public inquiry into his parish administration in 1826, and to promote the prosecution of O'Sullivan for libel at the Limerick assizes of July 1831. There is no evidence that he maintained, as legend had it, the custom of jus primae noctis on the estate. O'Sullivan and the knight were reconciled in 1844, and Fitzgerald carried the priest's coffin at his funeral in 1850.
Fitzgerald would have grasped without difficulty the defamatory verses popular in the village, as he was a fluent Irish-speaker and notable scholar in medieval Gaelic poetry, a member of the RIA from the 1820s, and friendly with the scholar Eugene O'Curry (qv) in the 1840s. He was a founder member of the Irish Archaeological Society in 1841. Though approving the removal of anti-catholic penal legislation in 1829, and liberal in social principle, he was hostile to the repeal campaigns of the 1830s and 1840s, but was never sufficiently attracted to politics to enter an election. He was infected with cholera while attending Glin workhouse on 25 April 1854 and died within hours.
He married (28 July 1812) Bridgetta Eyre of Westerham, Kent; they had two sons and two daughters. He fathered a number of children outside marriage.