Macraith Mág Tighearnán (anglicised Magrath McKiernan) was chief of the McKiernan Clan and Baron or Lord of Tullyhunco barony, County Cavan from c.1240 until his death in 1258.
Macraith was the son of Tighearnán who was son of Conbuidhe.
On the death of the previous chief, Duarcán Mág Tighearnán, Macraith took the chieftaincy and resided in the castle of Croaghan of the Cups (Irish- Cruachan O'Cúbhrán), besides the modern town of Killeshandra. He acknowledged Felim Ua Conchobair, King of Connacht from 1233 to 1265, as his overlord and gave him his sons as hostages. McKiernan's lands of Tullyhunco were on the border between the O'Rourke and O'Reilly clans and the McKiernans were in conflict with both clans who were trying to assert their authority over them.
The Annals of Connacht for the year 1256 state-
After the battle of Magh Slécht, Fedlim O Conchobair and his son Aed na nGall, with the men of Connacht, and Tigernan O Ruairc, with the men of Brefne, made an expedition to Loch in Trein; and the two armies fell upon the churches of Brefne, all except Fenagh, and returned to their homes with hostages of the Fir Brefne, that is, of Mac Fiachrach and Mac Tigernain and Mag Samradain and of the son of Art O Ruairc; and Fedlim gave the hostages of the chieftains into the custody of O Ruairc and handed over Mag Samradain to his own son, Aed na nGall. Conchobar son of Tigernan O Ruairc, king of Brefne, and Gilla na Naem Mag Samradain and Mac Raith Mag Tigernain, the son of Cu Buide, and Mac na hOidche Mag Dorchaid and Cathal Mag Ragnaill and the sons of the kings and chieftains of the Ui Briuin with their followers came to Fenagh to meet with Domnall O Raigillig. They pursued him from the meeting-place and killed his beloved son Annad and Gilla Isa Mac in Chrottaig (Son of the Hunchback) [O Raigillig?] and many others. Next day, St. Brendan's day, they took a great prey out of Cruacha O Cubrain and plundered the country all the way to Fenagh. That day was ‘a drop before a shower’ to the Muinter Raigillig, since from it proceeded the beginning of the harm and harassing that afterwards befell them. For it is then that they sent envoys to the Connacht Galls, Macwilliam Burke and Mac Gosdelb, [inviting them] to destroy Connacht and Brefne.