Washington Township is one of nine townships in Decatur County, Indiana. As of the 2020 census, its population was 14,053 (up from 13,304 at 2010) and it contained 6,177 housing units.
Washington Township was organized in 1822.
Strauther Pleak Round Barn was added to the National Register of Historic Places in 1993.
According to the 2010 census, the township has a total area of , of which (or 99.69%) is land and (or 0.31%) is water.
(This list is based on USGS data and may include former settlements.)
The township contains five cemeteries: Forsythe, Saint Marys, Sand Creek, South Park and Springer.