ILLTYD or ILTUTUS (fl. 520), sometimes called Illtyd Farchog, or The Knight, Welsh saint, was born in Brittany, being the son of Bicanys, by a sister of Emrys Llydaw called Riengulida, and therefore a great-nephew of St. Germanus [q. v.], bishop of Auxerre, whose disciple also he was. The oldest, and probably on that account the most trustworthy, account of his life is to be found in the lives of SS. Gildas, Samson, and Maglorius, which were written about 600 or soon after, and are published in Mabillon's `Acta Sanctorum Ordinis S. Benedicti,' Venice, 1733, i. 131, 154 sqq., 209 (see also Liber Landavensis, p.287, for the life of St. Samson). Here the name is variously given as Hildutus and Eltutus, and it is stated that he had a school on a small and barren island, which was, however, joined to the mainland in answer to his prayers, and became known as Llanilltyd Fawr, which is the Welsh form for Llantwit Major in Glamorganshire. Gildas, Samson, bishop of Dol, and Maglorius, Samson's successor at Dol, are said to have been at Illtyd's school. Owing, perhaps, to a misreading of the life of St. Samson, it is erroneously stated in the 'Life of St. Pol de Leon,' written in 884 (published in (Revue Celtique,' v. 413-60), that the school was in Caldey Island.
Fuller details of Illtyd's life are given in Cottonian MSS. Vespasian, A. xiv., a manuscript written in the eleventh or twelfth century, printed indifferently in Rees's 'Cambro-British Saints,' pp. 465-94, and abridged in Capgrave's 'Nova Legenda Angliæ,' fol. clxxxvii. It is there related that Illtyd in his early days took to the profession of arms, crossed from Brittany to the court of King Arthur, afterwards came to Glamorgan, and attached himself for a time to the court of the regulus of that district. On one occasion he joined the king's family in a hunt, in course of which the territory of St. Cadoc [q.v.] was entered upon, and all excepting Illtyd are said to have been miraculously swallowed up by the earth for insulting Cadoc, who then easily succeeded in inducing Illtyd to renounce the world and to devote himself to religion (see 'Life of St. Cadoc' in Rees's Cambro-British Saints, p.337; Capgrave, loc. cit.; Walter Mapes, De Nugis Curialium, ed. Wright for Camd. Soc., p.76). Submitting to the tonsure and assuming the clerical habit, he was ordained by Dubricius, bishop of Llandaff. He built a church, and afterwards a monastery, which may be identified with the school already referred to, at Llantwit Major, under the patronage of Meirchion, a chieftain of Glamorgan (cf. Liber Landavensis, p.320). He attracted a number of scholars to him, especially from Brittany, including, in addition to those mentioned in the earlier biography, St. David, St. Lunarius, and St. Paul Aurelian, otherwise St. Pol de Leon. The college continued to flourish for several centuries, sending forth a large number of missionaries until, early in the twelfth century, its revenues were appropriated to the abbey of Tewkesbury (Clark, Cartæ et Munimenta de Glamorgan, i. 21). Besides teaching his pupils, Illtyd is said to have worked with his own hands; to have been specially skilful in agriculture, and to have reclaimed a large portion of land from the sea (Capgrave, loc. cit.), which may be the explanation of the miracle which is alleged to have united the island to the mainland. Later writers assert that he introduced improved methods of agriculture, and invented a new kind of plough. The story of Illtyd's life is the subject of a poem by Lewis Morganwg (fl. 1520) (Iolo MS. ff. 292-5). According to Cressy, his commemoration was held on 7 Feb., but the year in which he died is uncertain. At least twelve churches, seven of which are still called after his name, are dedicated to Illtyd in different parts of Wales; most of those in Glamorganshire were probably founded by him, as Llantwit Major, where a cross bearing an inscription to the memory of Iltet, Samson, and Ebisar, and erected about the ninth century, is still to be seen. It is engraved in Westwood's 'Lapidarium Walliæ,' pl. 4, and in Hübner's `Inscriptiones Christianæ,' p.23, where also is to be found Professor Rhŷs's reading of the inscription, which differs from that given in Haddan and Stubbs's `Councils,' i. 628.
[Authorities cited above; Archæologia Cambrensis, 5th ser. v. 409-13; The Antiquities of Llantwit Major, by Dr. Nicholson, published in Williams's Monmouthshire, pp. 45-53; Rees's Welsh Saints, pp. 178-80.]