Causantín mac Fergusa

Causantín or Constantín mac Fergusa (English: "Constantine son of Fergus") (before 775–820) was king of the Picts (or of Fortriu), in modern Scotland, from 789 until 820. He was until the Victorian era sometimes counted as Constantine I of Scotland; the title is now generally given to Causantín mac Cináeda. He is credited with having founded the church at Dunkeld which later received relics of St Columba from Iona.

It had been proposed that Causantín and his brother Óengus were sons of Fergus mac Echdach, King of Dál Riata, but this is no longer widely accepted. Instead, it is thought they were kin to the first king Óengus mac Fergusa, perhaps grandsons or grandnephews. This family may have originated in Circinn (presumed to correspond with the modern Mearns), and had with ties to the Eóganachta of Munster in Ireland.

Causantín's reign falls in a period when Irish annals have relatively few notices of events in Scotland, possibly due to the failing of the annals believed to have been kept in Scotland at Iona and Applecross. Perhaps for that reason, there are only two reports which mention him. Other entries make it clear that the Vikings were active in Ireland and on the western coasts of Scotland in this time, which may also account for the lack of records. Iona was a target, and it may be that Abbot Noah of Kingarth, on the Isle of Bute, was killed by raiders.

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