The Three Collas were three brothers, sons of Eochaid Doimhlen, son of the High King Cairbre Lifechair (son of Cormac mac Airt), who are credited with establishing the kingdom of Airgialla in north-eastern Ireland in the 4th century. Cairbre was married to Aine Ingen Finn and Fionn mac Cumhail is said to have died during his reign. The Three Collas went into exile in Alba (Scotland), because their mother was a daughter of the king of Alba. The Scottish MacDonald clan trace their ancestry to Colla Uais. They destroyed Emain Macha, which was never again used as the capital of Ulster. They were:
- Cairill, aka Colla Uais ("noble")
- Áed, aka Colla Menn ("the stammerer")
- Muiredach, aka Colla Fo Críth
The three brothers all bore the name of Colla - Colla Uais, Colla Meann, and Colla da Crioch. The designation Colla was "imposed on them for rebelling," and means strong man, their original names being Cairsall, Aodh and Muredach. Colla da Chrioch became the first king of Airghialla (Oriel). The tribes of the three Collas were known as the Airghialla and included the Uí Cremthainn, Mughdorna, Uí Meath, Airthir, Uí Tuirte, Uí Meic Uais, and Gernmhaighe, among others. Noted chiefs of Airghialla included O'Carroll, O'Boylan, O'Heany or Hegney, O'Leighnin, O'Rogan. The MacDonalds descend from Colla Uais- one of the three. The MacAlisters of Londonderry were a Scottish sept with Irish Gaelic origin back to Colla Uais, the eldest of the three Collas. The countries of Ely O'Carroll and Hy Carthin comprised some of the north-western portion of Ossory and Thomond (Offaly, Kilkenny, Queen's County-Leix). O'Carroll was the head of the Clan Cian race, as the MacCarthys were of the Eugenians: and the O'Briens, of the Dalcassians. The lands of the southeast (Ossory, Clare; Desmond) were possibly the territories of the Uí Bairrche (Uí Bearchon, aka Ibercon), the Uí Dheaghaidh (O'Dea, aka Ida), and the Uí Crinn (Uí Grine, aka Igrin).