Forth Fothairt (Irish)
Barony
Country	Ireland
Province	Leinster
County	Carlow
Area
• Land	159.89 km2 (61.73 sq mi)

Forth (Irish: Fothairt) is a barony in County Carlow, Ireland.

Forth takes its name from the Irish Fortuatha, a term that described a region (tuath) not ruled by members of the dominant dynasty of a province. In this case, the region was known as Fothairt Mag Feá, "the fothairt of the plain of beeches."

Forth is found in the eastern part of County Carlow. Physical features include the Burren River and Mount Leinster.

Forth barony is bordered to the east by St. Mullin's Upper; to the north by Rathvilly; to the west by Idrone East; to the northwest by Carlow (all the preceding baronies are also in County Carlow); to the northeast by Shillelagh, County Wicklow; and to the southeast by Scarawalsh, County Wexford.

Uí Nualláin (O'Nolan) were rulers of Fothairt Mag Feá.^[1]

Below is a list of settlements in Forth barony:

• Aghade
• Ballon
• Myshall