Cass Township is one of fifteen townships in Greene County, Indiana, USA. As of the 2020 census, its population was 299, down from 358 at 2010.

Historical population

Census	Pop.	Note	%±
1890	847		—
1900	899		6.1%
1910	860		−4.3%
1920	756		−12.1%
1930	634		−16.1%
1940	670		5.7%
1950	603		−10.0%
1960	447		−25.9%
1970	426		−4.7%
1980	418		−1.9%
1990	386		−7.7%
2000	392		1.6%
2010	358		−8.7%
2020	299		−16.5%
Source: US Decennial Census

According to the 2010 census, the township has a total area of 18.08 square miles (46.8 km), of which 17.62 square miles (45.6 km) (or 97.46%) is land and 0.45 square miles (1.2 km) (or 2.49%) is water. The streams of Doans Creek, Gilbert Creek, Mud Creek and Woodhouse Branch run through this township.

• Newberry

• Taylor Township (east)
• Madison Township, Daviess County (southeast)
• Elmore Township, Daviess County (southwest)
• Vigo Township, Knox County (west)
• Washington Township (northwest)

The township contains three cemeteries: Gilbreath, Old Slinkard and Slinkard.

• Indiana State Road 57

• "Cass Township, Greene County, Indiana". Geographic Names Information System. United States Geological Survey, United States Department of the Interior. Retrieved September 24, 2009.
• United States Census Bureau cartographic boundary files

• Indiana Township Association
• United Township Association of Indiana