Middle Third or Middlethird (Irish: An Trian Meánach[1]) is a barony in County Waterford, Ireland.

[2] A "third" (trian) was an old Irish land division of variable extent.

[3] Middle Third is located in the east of County Waterford, south of the River Suir and west of Gaultier.

It also contains Bilberry Rock, site of a feral goat herd for centuries.

Some of Middle Third was anciently part of the Viscount Doneraile's estate.