The Uaithni were a people of early Ireland, who in early medieval times lived in north-eastern County Limerick

County Limerick

It is thought that humans had established themselves in the Lough Gur area of the county as early as 3000 BC, while megalithic remains found at Duntryleague date back further to 3500 BC...

 and the adjoining part of County Tipperary

County Tipperary

County Tipperary is a county of Ireland. It is located in the province of Munster and is named after the town of Tipperary. The area of the county does not have a single local authority; local government is split between two authorities. In North Tipperary, part of the Mid-West Region, local...

, and had traditions that they once lived west of the River Shannon

River Shannon

The River Shannon is the longest river in Ireland at . It divides the west of Ireland from the east and south . County Clare, being west of the Shannon but part of the province of Munster, is the major exception...

. Their name derives from a reconstructed Proto-Celtic *Autēniī, and they have been identified as the Auteini (Αύτεινοι) referred to in Ptolemy

Ptolemy

Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

's 2nd century Geography as living in approximately County Galway

County Galway

County Galway is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the city of Galway. Galway County Council is the local authority for the county. There are several strongly Irish-speaking areas in the west of the county...

.

Two branches of the Uaithni are known: the Uaithni Cliach, corresponding to the later barony of Owney in County Limerick, and the Uaithni Tire, corresponding to the barony of Owneybeg in County Tipperary. The Annals of the Four Masters

Annals of the Four Masters

The Annals of the Kingdom of Ireland or the Annals of the Four Masters are a chronicle of medieval Irish history...

record the death of Ainle, son of Cathan, lord of the Uaithni Cliach, killed by Vikings in AD 914; of Dubhdabharc, son of Maelmordha, lord of the Uaithni Tire, in 949; of Eochaidh Ua Loingsigh, lord of the Uaithni Tire, in 1080; and of Cuilen Ua Cathalan, lord of the Uaithni Cliach, in 1107.