Ballintober South (), also called Ballintober West, is a barony in County Roscommon, Ireland.
Ballintober South is named after Ballintober town; however, it does not actually contain that town, which is located in Castlereagh barony.
Ballintober South is located in the centre of County Roscommon, northwest of Lough Ree.
The àManacháin (O'Monaghans) were lords of the "Three Tuathas", and in AD 866 were rulers of this area, known as Ui Briuin na Sionna (O'Brien of the Shannon). In 1249, they were overthrown by the O'Beirnes (àBirn).
The O'Mooneys were chiefs of Clann-Murthuile, also believed to be in Ballintober South.
Below is a list of settlements in Ballintober South: