In medieval Ireland, the kings of Mide were of the Clann Cholmáin, a branch of the Uí Néill. Several were High Kings of Ireland. After the collapse of the kingdom in the 12th century its dynasty, the Ua Mael Sechlainn or Ó Melaghlins, were forced west and settled on the east bank of the Shannon. Bearers of the name were still noted as among the Gaelic nobility until as late as the 1690s, though they had lost any real power long before.
The Kingdom of Mide itself seems to have existed as a kingdom (though of varying sizes) since at least the early historic era. Its name means "middle", denoting the fact that it was situated in the very centre of Ireland in what is now County Westmeath, parts of north County Offaly, south County Longford and western County Meath. Its early kings may have been of the Dál Messin Corb - whose sept, the Uí Garrchon, were Kings of Leinster. However, from the late 400's onwards they were driven away from their original homeland in northern Leinster and over the Wicklow Mountains by the Ui Néill, whose sept, the Clann Cholmáin, took their place.