Cummascach mac Flainn (died 757) was a king of the Uí Failge, a Laigin people of County Offaly.
He was one of the many sons of Fland Dá Chongal, a previous king.
[1] He ruled from 755 to 757.
[2] He was the first of Fland's sons by Érenach, daughter of Murchad Midi (died 715) of Uisnech to hold the throne.
[citation needed] Not mentioned in the Annals of Ulster, the Annals of Tigernach record that he was slain in 757 by Máel Dúin mac Áedo (died 786), King of Munster.