Union Township is one of four townships in Ohio County, Indiana, United States. As of the 2020 census, its population was 447, and it contained 203 housing units.
According to the 2010 census, the township has a total area of , of which (or 99.22%) is land and (or 0.78%) is water. Union is the smallest township in the state by area.
(This list is based on USGS data and may include former settlements.)