Magh Adhair (Irish pronunciation: [ˌmˠaː ˈəiɾʲ]; "Adair's plain") is a former inauguration site and place of archaeological significance located near the village of Quin, County Clare, in Ireland.

It is stated, in both Frost's History and Topography of the County of Clare and in O'Donovan & O'Curry's ordnance survey letters of 1839, that the mound received its name from a chieftain of the Fir Bolg, Adhair, (Aed) the son of Umor and brother of Aengus, who was reputedly responsible for building the cliff-fort of Dun Aengus on the Aran Islands.

Once Clare was colonised by the Gaelic Milesians, sometime between the late Iron Age and the coming of Christianity in the 5th Century, (it has been suggested sometime circa 100AD) Magh Adhair became the ceremonial consecration ground of the Kings of Thomond for the North Munster peoples known as the Dal gCais.

[citation needed] Entries and poems for several O'Brien inaugurations (1242, 1267, 1277 and 1311) at Magh Adhair are found in the Caithreim Thoirdhealbhaigh, an account of the conflict between the Anglo-Norman insurgents and Gaelic nobility of Thomond in the 13th and 14th centuries, such held for the De Clare candidate of Clan Brian in 1311 — His chiefs assembled around Dermot, the son of Donogh, who was son of Brian Roe O'Brien at Moy Eyre to invest him with the chieftainship, and the tower-like hero was solemnly inaugurated.

Dermot of Dun Mor The mild, lively, fierce, Received the hostages Through his wisdom and sword His gracious smile and pomp He exhibits with grace And since he has commenced his career His fame has spread afar Momonia of Bards Is his principality Proclaim we him King Of his tribes with great joy.

Adjacent to this, to the west, is a satellite mound or cairn, notably stonier and smaller in its dimensions than the central structure, the latter of which is made largely of soil.