Fairmount Township is one of thirteen townships in Grant County, Indiana, United States. As of the 2010 census, its population was 4,239 and it contained 1,909 housing units.
According to the 2010 census, the township has a total area of , of which (or 99.87%) is land and (or 0.10%) is water. The streams of Back Creek, Winslow Ditch, Barren Creek, Fowlerton Drain, New Prairie Creek and Van Run run through this township. Lake Galatia, the southernmost natural lake in Indiana, lies in this township.
The township contains two cemeteries: Bethel and Park.
The township is in Madison-Grant United School Corporation. The district's comprehensive high school is Madison-Grant High School.
Fairmount Township residents may obtain a free library card from the Fairmount Public Library in Fairmount.