Middle Third (Irish: An Trian Meánach; also spelled Middlethird) is a barony in County Tipperary, Ireland.
Baronies were created after the Norman invasion of Ireland as divisions of counties and were used the administration of justice and the raising of revenue.
The entry in the Annals for 1118 reads, " A hosting by Toirdhealbhach Ua Conchobhair, king of Connacht, and by Murchadh O Maelsechlainn, king of Temhair, along with him, and by Aed O'Ruairc, into Mumha, as far as Glenn-Maghair; and he gave Des-Mumha to Mac Carthaigh, and Tuadh-Mumha to the sons of Diarmaid Ua Briain, and carried off the hostages of each."
With this 12th-century division of Munster into two parts, Thomond included the area about the diocese of Killaloe, and additionally encompassed the traditional territories of Úi Fidgeinti, Uí Chonaill Gabra, Eóghanacht Áine, Éile, Corco Mruadh, the tribes of Uaithne (later held by the Síl Cennétich, and much of Eóghanacht Caisel and Ciarraige Luachra.
When the Penal Laws were sufficiently relaxed, the Roman Catholic archbishops returned openly to the see, but changed their residence and cathedra to Thurles.
However, the neighbouring barony of Kilnamanagh was split into Upper and Lower half-baronies, being allocated to the north and south ridings respectively.