Tonnagh Beg is a townland in County Tyrone, Northern Ireland.
It is situated in the barony of Clogher and the civil parish of Donacavey and covers an area of 227 acres.
[1] The name derives from the Irish: Tamhnach beag (Little green field or little field).
[3] The townland contains Tonnagh Beg bog, a 55.6-hectare (137-acre) designated Area of Special Scientific Interest (ASSI).
It is a large lowland raised bog, among the best examples in the west of Northern Ireland.