Fleming, Thomas (1593–1651), Franciscan, catholic archbishop of Dublin, was the third son of William Fleming (qv), 14th Baron Slane, and his wife and third cousin Elinor, youngest daughter of Thomas, 13th Baron Slane. Around 1610 he left Ireland for the Franciscan monastery of St Anthony at Louvain. There he studied theology under Father Aodh Mac Cathmhaoil (qv), and his progress was so rapid that he was made professor of theology before his ordination on 31 March 1618. He remained as professor at Louvain until his nomination to the see of Dublin on 23 October 1623. Before his consecration in December of that year, Fleming obtained letters apostolic from Urban VIII assuring papal protection and patronage for the Irish colleges on the continent, and sanctioning and facilitating the mission to Ireland. Fleming acted as a patron of Irish literary endeavours, supporting scholars such as Luke Wadding (qv), Mícheál Ó Cléirigh (qv), and Stephen White (qv). He championed the fledgling Capuchin mission to Ireland, despite his initial opposition to attempts by his cousin Francis Nugent (qv) to found a house in Dublin.
On assuming his post, the new archbishop was criticised for alleged partiality towards members of his own order, and Paul Harris (qv), a secular priest in the diocese, launched a bitter onslaught against him in his Olfactorium and other writings. A number of his episcopal contemporaries defended Fleming's integrity in 1626 and again in August 1636 at an assembly of the religious orders in Ireland. Controversy with Harris persisted until 1634 when the Sacra Congregatio de Propaganda Fide intervened; however, as late as 1636 Fleming wrote to Wadding requesting assistance in the suppression of Harris's works.
Fleming presided over a provincial synod at Kildare in July 1640. He selected Joseph Everard to represent him at the May 1642 Kilkenny clerical synod, convened in response to the outbreak of hostilities the previous October, and he attended the first meeting of the Catholic Confederate Association in October 1642, appointing Dr Edmund O'Reilly (qv) vicar general of the diocese of Dublin in his absence. Active in the association in its early years, he sat on the supreme council between 1642 and 1645 and as a supernumerary in 1647. His behaviour throughout the decade reflected an underlying desire for peace, tempered with an obligation to obey his religious superiors. He rejected offers of money and ammunition from the papal delegate, PierFrancesco Scarampi (qv), in July 1643, but in August that year wrote to Urban VIII thanking him for sending a representative to Ireland. In August 1644 he was among those nominated to negotiate with James Butler (qv), marquess of Ormond, despite the latter's protestations against the archbishop. However, the lack of evidence of any active participation in negotiations suggests his selection was largely symbolic.
Fleming aligned himself with the papal nuncio, GianBattista Rinuccini (qv), in rejecting the first Ormond peace in 1646, and was eclipsed on the supreme council by younger prelates after the upheavals of that year. As the association edged towards a truce with Inchiquin (qv) in May 1648, Fleming was among four bishops who, along with the nuncio, were empowered to act on behalf of the Irish episcopate. However, Rinuccini criticised him the following month for a willingness to side with the peace party. Nevertheless when the nuncio pronounced his controversial excommunication, Fleming wrote to the bishop of Ossory, commanding him to enforce the interdict. For the greater part of 1649 he resided in his diocese, and was at the clerical assembly at Clonmacnoise in December, which declared oblivion of all past differences. On 6 June 1650 he wrote describing the devastation wrought in Dublin – priests killed, religious put to flight, and many people perishing from war and famine. With the nullification of the confederate peace, he adhered to Ormond's excommunication at Jamestown in August 1650, and was at Galway on 5 October that year, to sign a document authorising Nicholas French (qv) and Hugh Rochfort to negotiate with any catholic ruler or state for the preservation of religion. He died at Galway on 2 August 1651. There is a fresco of Fleming on the wall of the aula of St Isidore's College, Rome.