Constantine, son of Cuilén (Mediaeval Gaelic: Causantín mac Cuiléin; Modern Gaelic: Còiseam mac Chailein), known in most modern regnal lists as Constantine III) was king of Scots from 995 to 997. He was the son of Cuilén, King of Scotland (Cuilén mac Iduilb). John of Fordun calls him, in Latin, Constantinus Calvus, which translates to Constantine the Bald. Benjamin Hudson notes that insular authors from Ireland and Scotland typically identified rulers by sobriquets, noting for example the similarly named Eugenius Calvus (Owen the Bald), an 11th-century King of Strathclyde.
Constantine is not known to have any descendants and he was the last of the line of Áed (Áed mac Cináeda) to have been king. With his death, the rivalry between descendants of Causantin and Áed gave way to a rivalry between two new royal lines, both descended from Causantin. One line descended from Kenneth II and was represented by his son Malcolm II. The other line descended from his brother Dub, King of Scotland (reigned 962-967) and was represented by Kenneth III.