GILLE or GILLEBERT (fl. 1105–1145), bishop of Limerick, termed by Keating Giolla Easbog, was consecrated in Ireland, but it is uncertain whether he was an Irishman or a Dane, Limerick being then a Danish city. If he were abbot of Bangor, as Lanigan thought, he would probably have been an Irishman, but Keating, to whom Lanigan refers, does not say so. He had travelled abroad, and became acquainted with Anselm at Rouen. Their friendship continued, and on his appointment to Limerick he appears to have written of it to Anselm. A correspondence followed, which may be seen in Ussher's ‘Sylloge.’ In his letters Anselm urged Gille to use all his influence to abolish certain ecclesiastical usages which prevailed in Ireland, referring among other things to the appointment of bishops ‘contrary to the order of ecclesiastical religion,’ and to consecration by a single bishop, and in places where bishops ought not to be. For these he wished, as Lanigan observes, to substitute the Roman usages. In compliance with Anselm's advice, Gillebert first attempted to introduce the Roman liturgy instead of the various liturgies in use from time immemorial in Ireland, and which he calls ‘schismatical,’ an expression which, as Lanigan says, only showed his ignorance. In pursuance of this design he wrote a tract entitled ‘Of the Ecclesiastical Use’ (or order of divine service). This, which appears to have been merely a copy of the Roman liturgy and office, has not come down to us, though the treatise on ‘Church Organisation’ which he prefixed is extant, and has been published by Ussher. In the latter he describes the hierarchy of the Roman church, and illustrates the gradations of dignity by a comparison with the corresponding secular ranks. The ascending series terminates with the pope, whose correlative is the emperor of Rome; but as the Irish had nothing to do with the empire the foreign character of the system was apparent. This treatise appears to have been written before he became legate, but the date of his appointment to that office is not known.
A further step towards the introduction of the Roman system was the holding the council of Rathbreasail, in which it was proposed to divide Ireland into twenty-six dioceses, the boundaries of which were set out in full detail. There has been much discussion as to the identity of this synod, which is not mentioned in the ‘Annals,’ and is only found in Keating, who took it from the lost ‘Book of Clonenagh.’ Mr. King thought it was the same as the synod of Fiadh mic Aenghusa, but they are expressly distinguished by Keating, though he allows that they were held about the same time, i.e. about 1111; and Mr. King was in error as to the situation of Fiadh mic Aenghusa, which, according to the ‘Annals of Lough Cé,’ was near Uisnech in West Meath. Another synod in this latter place was also supposed by Colgan to have been identical with that of Fiadh mic Aenghusa, and thus there would have been only a single synod. There is no doubt, however, that there were really three, held about the same time. That of Uisnech was a mere assembly of the local clergy to rearrange the parishes of West Meath. The synod of Fiadh mic Aenghusa was an important one, at which King Muircheartach was present and a large number of bishops, clergy, and laity. But the synod of Rathbreasail (at Mountrath in Queen's County) was an ecclesiastical assembly at which no layman of importance was present, and the president of which was Gillebert, the other names mentioned being Ceallach or Celsus, the primate, and Maelisa mac Ainmire, termed by Keating ‘noble bishop of Cashel,’ but in the ‘Annals of the Four Masters’ bishop of Waterford. There were therefore present the bishops of two Danish cities with Celsus, a favourer of the new ideas, who thus combined to revolutionise the constitution of the Irish church. But no immediate result followed. It was merely an arrangement on paper, and Gillebert was as unsuccessful in this as in his attempt to supersede the Irish liturgies. In both cases the current of national feeling was against him. This synod is remarkable as the first over which a papal legate presided, Gillebert having been the first holder of the office, and also as the first Irish synod which closed its proceedings in Roman fashion with an anathema.
Gillebert died, according to the ‘Chronicon Scotorum,’ in 1145.[Lanigan's Eccl. Hist. iv. 37–43; King's Primacy of Armagh, pp. 30, 81–5; Ussher's Sylloge (Works, iv. 500–14); Keating's Forus Feasa, Reign of Muircheartach; Reeves's Eccl. Antiq. pp. 139–41, 162; Annals of Four Masters, A.D. 1111; Chron. Scot. A.D. 1107–45.]