Constantine I of Scotland

Causantín mac Cináeda, counted as Constantine I (c. 836–877), was a son of Kenneth MacAlpin who succeeded his uncle Domnall as king of the Picts in 862. His reign was dominated by Viking attacks: in 870 Norse leaders sacked Dumbarton Rock, stronghold of Alt Clut.

Two years later Causantín had its fugitive king Artgal killed. After a defeat near Dollar in 875, he fell fighting Vikings in Fife in 877, reportedly beheaded, and was buried on Iona.