Cinhil ap Domnall, also known as Cinhil Ru, was the ancient Alban tribal king who united the warring tribes of the Cruithne and forged a treaty with the Dalriada of Eire. United under Cinhil Ru's banner, the people of Alba and Eire joined together and drove back the invading armies of Tiberium who occupied Alba. According to Ferghus of the Maghuin Dhonn, he achieved the feat by spreading false stories of bears that fed on children and telling his people the Maghuin Dhonn had gone mad, sacrificing their diadh-anam, and the same fate would befall their people if they did not join together.
After freeing Alba from the Tiberians, Cinhil Ru became the first Cruarch of Alba and Drustan mab Necthana's line was descended from him.