Frosinone, John de (d. c.1274), papal legate and collector of ecclesiastical revenues in Ireland, was sent to Ireland by Innocent IV on 16 March 1249 to supervise the collection of the triennial tenth agreed at the general council of Lyons in 1245 for the relief of the Holy Land. He had the cooperation of Henry III in his mission and was granted a canonry in St Patrick's cathedral, Dublin. His diligence in carrying out his duties aroused the ire of a number of Irish prelates who objected to Irish ecclesiastical revenues leaving the country. In 1249 Hubert de Burgh (d. 1250), bishop of Limerick, persuaded the bishops of Achonry and Killala to excommunicate Frosinone for his activities, but this was deemed uncanonical as a papal nuntius could only be excommunicated by the pope. Indeed Innocent guaranteed that as long as Frosinone remained in papal service, he would not be subject to any censure but that of Rome.
In 1251 Frosinone travelled to England to report on his progress to Henry III and was granted an annual stipend of 20 marks from the English exchequer. His mission was reported as extraordinarily successful; in February 1252 he was appointed a papal chaplain. However, clerical complaints to Rome of his corruption (he was alleged to have embezzled 2,000 marks) led to the appointment of a papal inquisition, which quickly dismissed the allegations when it became apparent Frosinone had done no more than take his commission. But he came under increasing pressure from Henry III, desperate for cash to finance an expedition to Gascony, to borrow unconditionally from the funds. By 1254 some money had been legitimately diverted to the English crown after Henry took the crusader's oath. In August that year Frosinone was deputed to promote the crusade in Ireland and collect the new ecclesiastical tenth on English and Irish ecclesiastical revenue granted to the king. By December Frosinone had nominated a deputy, Laurence Somercote, in Ireland, and had gone to collect the tax in Scotland. Frosinone's success in Ireland proved illusory; when the papacy demanded delivery of the revenues collected, the Italian's successors realised that he had been far from a meticulous keeper of records. Apparently he had deposited much of the money in various religious houses throughout Ireland, and the new collectors did not know where and how much. Naturally they could expect little assistance from Irish clerics so hostile to the tax, and, despite numerous threats of dire ecclesiastical censure, the sum finally paid to Rome was paltry. Frosinone appears to have died in Ireland in 1274.