Causantín mac Cuilén

Constantine III
17th-century portrait of Constantine, when he was reckoned as Constantine IV
King of Alba
Reign	995–997
Predecessor	Kenneth II
Successor	Kenneth III
Born	c. 970
Died	997 Rathinveramond near Perth
Burial	Iona
House	Alpin
Father	Cuilén, King of Alba

Constantine, son of Cuilén (Mediaeval Gaelic: Causantín mac Cuiléin; Modern Gaelic: Còiseam mac Chailein), known in most modern regnal lists as Constantine III, (born c. 970–997) 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.

The Scottish monarchy of this period based its succession system on the rule of tanistry. All adult male descendants of previous monarchs were eligible for the throne. The kingship regularly switched from one line of royal descendants to another, though they were all closely related. Constantine was able to rise to the throne, despite his cousin and predecessor having a son of his own. The next two kings (Kenneth III, Malcolm II) were his cousins, and killed their respective predecessor to gain the throne. The succession rule had the benefit of ensuring that there would always be an adult king on the throne, avoiding the usual problems of minority reigns. The various kings had their lands and power bases in different areas of Scotland, preventing any single region from claiming full domination of the others. This may have helped the country avoid significant secession movements. The downside was that any single king had to face adult rivals for the throne. His kinsmen had their own ambitions and would not wait for his death from natural causes to achieve them. The succession was often decided through acts of warfare and murder, resulting in early deaths and high casualty rates in the extended royal family.