Clay Township is one of nine townships in Decatur County, Indiana. As of the 2020 census, its population was 1,284 (slightly down from 1,287 at 2010) and it contained 523 housing units.
Clay Township was organized in 1836.
Champ's Ford Bridge was added to the National Register of Historic Places in 2009.
According to the 2010 census, the township has a total area of , of which (or 99.86%) is land and (or 0.12%) is water.
(This list is based on USGS data and may include former settlements.)
The township contains seven cemeteries: Center Grove, Columbia, Mowery, Nauvoo, Patrick, Pumphrey and Swinney.