Saint Illtud's feast day and commemoration is celebrated on 6 November, but the great 'pardon of Ildut' at Locildut in Brittany is held on the last Sunday of July. According to legend, Illtud was buried west of the town of
Brecon, in the church of Llanilltud (sometimes called Capel Illtud, which was demolished in the late 20th century), on a tract of moorland known as
Mynydd Illtud. Near this church, there is a megalithic monument called
Bedd Gwyl Illtyd, or the "Grave of St. Illtud's Eve." Until comparatively recently, Illtud was honoured by the practice of ‘watching’ (keeping vigil) at this stone before his festival. The
Life tells of Illtyd's bell being recovered from the armies of King
Edgar the Peaceful and of Illtyd's protecting his people against the people of yr
Hen Ogledd in the time of
William the Conqueror. There is also a cross, probably of the ninth century, bearing the inscription: SAMSON POSUIT HANC CRUCEM PRO ANIMA EIUS ILITET SAMSON REGIS SAMUEL ERISAR – "Samson placed his Cross here for his soul, for the soul of Illtud, Samson, Rhain, Sawyl and Ebisar". There is no formal evidence for a cult of Illtyd surviving from before the 11th century. However, in Celtic countries it is the names of places that tell us most about the existence and veneration of the saints during the oldest times. and was the chief centre of the cult of Saint Illtud. In
Glamorgan many churches are dedicated to him, first and foremost
St Illtyd's Church, Llantwit Major, which stands on what is believed to have been the site of the monastery. Many other places are dedicated to him is because they belonged to the Llantwit monastery. Near to Llantwit itself are the villages of
Llantrithyd,
Llantwit Fardre, and
Llantrisant and at Newcastle and Bridgend churches are dedicated to Saint Illtud. In
Brecknockshire, the church at Llanhamlach east of
Brecon is dedicated to him, and lies south of a Megalithic grave called Ty Illtud, which was a site of mediaeval pilgrimage, the inside walls of the grave bearing incised crosses. The grave is thought to have been a retreat of Illtud, as was a similar megalithic monument Roc'h Ildut near Coadut (Coat Ildut/Coed Illtud/ Illtud's Wood) in Brittany, demolished in the 19th century. Llantrisant's three saints were Illtud, Gwynno and Tyfodwg. In Merthyr Tudful there are holy wells of Gwynno and Illtud. West of Brecon, the church of Llanilltud is on a mountain known as
Mynydd Illtud. Dedications in and around
Gower include Ilston, formerly Llanilltud Gwyr, Oxwich, a holy well of S. Iltut in Llanrhidian, Llanilltud Fach, or Llantwit-juxta-Neath and Pen-bre. A 13th-century church on
Caldey Island,
Pembrokeshire, is dedicated to Illtud. In
North Wales, there is a
Llanelltyd near Dolgellau. In Brittany, there are approximately 24, if other place-names like Aberildut are included; largely confined to the ancient dioceses of Leon, Treguier and Vannes, with small outliers in the region of Saint Malo, originally in the diocese of his pupil Samson. who is sometimes conflated with Illtud. ==Arthurian connections==