Cynog or Canog was the eldest son of Brychan, of Brecknock. Shortly after his birth he was committed to a holy man named Gastayn, by whom he was baptized. He is believed to have been murdered by Saxons at Merthyr Cynog, in Brecknockshire, in or about 492. This must have been in a piratical incursion. The torque or collar that his father gave him at his baptism was preserved at Brecon amongst its precious relics in the time of Giraldus Cambrensis. There are several churches in Wales dedicated to him, mostly in Brecknockshire. There is a church in Brittany that may bear his name, S. Cenneur, in the diocese of S. Malo.
Troparion of St Cynog tone 4
Spurred on by their impiety,/ God-hating barbarians sought to destroy thee, O holy Cynog,/ but by death thou didst gain the victory./ Pray for us, that we too may triumph over evil by faithfulness unto the end,/ that we may be granted great mercy.