Cornish chieftain and martyr (?). The Cornish tradition is that he was converted by Petroc, became a monk, and founded churches in Devon and Cornwall. These are recalled by two places in Cornwall called Constantine: one near Padstow, the other on the banks of the Helford river in SW. Cornwall. This was the larger of the two and survived as a monastery until the 11th century. He was also patron of the Devon churches of Milton Abbot and Dunsford.
There are also confused traditions in both Scotland and Ireland concerning Constantine, a king who became a monk. The Scottish tradition says that he was martyred at Kintyre in 576.
Feast in Cornwall and Wales: 9 March; in Scotland, 11 March.
G. H. Doble, The Saints of Cornwall, ii (1962), 15–24.