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.

[1] According to the 2010 census, the township has a total area of 11.61 square miles (30.1 km2), of which 11.52 square miles (29.8 km2) (or 99.22%) is land and 0.09 square miles (0.23 km2) (or 0.78%) is water.

[3] Union is the smallest township by area in the state.

(This list is based on USGS data and may include former settlements.)