Mulmosog is a townland located in the Barony of Banagh, within the Civil Parish of Inishkeel and the Electoral Division of Mulmosog, County Donegal.

It spans an area of 3,092,669 square metres, which equates to approximately 1.19 square miles or 764 acres.

Mulmosog shares its borders with Altnagapple to the north, Cashel and Meenavally to the west, Corker More and Crocknagapple to the east, and Meengilcarry and Tullinteane to the south.

The area is also known as Altnagapple.