John Macrory Magrath (born Munster, Ireland, in the 15th certury; date and place of death unknown) was, like many of his ancestors, chief historian to the O'Briens, princes of Thomond and chiefs of the Dál gCais clans. To the same family belonged the celebrated Miler Magrath, Protestant Archbishop of Cashel.
Magrath's fame rests on his one work, Cathreim Thoirdhealbhaigh. It was written in Irish, but has been translated into English by S.H. O'Grady. It is a history of the wars of Thomond from 1194 to 1318. Magrath has necessarily much to say of the Anglo-Normans, especially of the De Clares, and of the efforts made by the Dal gCais to repel their attacks. He has much also to say of the internal strife in Thomond, and he gives full particulars of the attempt of O'Brien and O'Neill in the thirteenth century to strike common cause against the invaders. But as neither chief would serve under the other the result was the victory of the Anglo-Normans at the battle of Downpatrick in 1259. We have also an account of the final overthrow of the de Clares at the Battle of Dysert O'Dea in 1318. The work says much about the Dal gCais chiefs, and of the topography of the districts over which they ruled.
This article incorporates text from a publication now in the public domain: d'Alron, E.A. (1913). "John Macrory Magrath". In Herbermann, Charles. Catholic Encyclopedia. Robert Appleton Company.