Upperthird or Upper Third[1] (Irish: Uachtar Tíre[2]) is a barony in County Waterford, Ireland.

Upperthird was originally called Uachtar Tíre, "upper country", referring to its high altitude (by Irish standards).

Tír became "third" presumably by analogy with Middle Third; "third" is commonly used to indicate Irish divisions of land, without any region being actually divided in three.

[5] This part of the Suir valley was the traditional territory of the O'Flanagan of Upperthird (Ó Flannagáin Uachtar Tíre).

Abraham Ortelius's map of 1602 shows the land belonging to the Aylward family (an Anglo-Norman surname, in Irish Aighleart).