Monaghan () is a barony in County Monaghan, Ireland.
Monaghan barony takes its name from Monaghan town (, "abounding in thickets").
Monaghan is found in central County Monaghan.
Monaghan barony is bordered to the north by Trough; to the southwest by Dartree; to the southeast by Cremorne (all the preceding are also in County Monaghan); to the east by Tiranny, County Armagh; and to the west by Magherastephana and Clankelly, County Fermanagh.
The MacMahons were chiefs in medieval times.
Below is a list of settlements in Monaghan barony: