Thomas Fleming (1593–1665) was an Irish Franciscan and Roman Catholic Archbishop of Dublin; he was entitled to hold the title Baron Slane, but renounced it.
His appointment gave great offence to opponents of the religious orders, and a bitter onslaught was begun against the new archbishop by the priest Paul Harris, in his Olfactorium and other brochures.
When the Irish Rebellion of 1641 broke out (1641–1642) the archbishop, though by inclination a man of peace, felt constrained to take sides with the Confederates and despatched a procurator to represent him at the synod of the clergy held in Kilkenny (May 1642).
In 1649, when all was lost, and the defeated Irish were confronted with Oliver Cromwell, a reconciliation was effected with Ormonde at a synod of bishops, a step which Archbishop Fleming favoured.
In appearance, he was described unkindly by Thomas Wentworth, 1st Earl of Strafford as a fat, red-faced man, dressed in a plain black suit, who looked more than a merchant selling cloth at Leadenhall Market than a bishop.