Mill Township is one of thirteen townships in Grant County, Indiana, United States. As of the 2010 census, its population was 10,882 and it contained 4,809 housing units.
According to the 2010 census, the township has a total area of , of which (or 99.96%) is land and (or 0.04%) is water. The streams of Bean Run, City Run, Ethel Run, Long Branch, Octain Creek, Regular Run and Shell Run run through this township.
The township contains two cemeteries: Riverside and Walnut Creek.
Mill Township residents may obtain a library card from the Gas City-Mill Township Public Library in Gas City.