Casner Township is one of sixteen townships in Jefferson County, Illinois, USA.

As of the 2010 census, its population was 1,239 and it contained 510 housing units.

[2] According to the 2010 census, the township has a total area of 36.02 square miles (93.3 km2), of which 35.98 square miles (93.2 km2) (or 99.89%) is land and 0.04 square miles (0.10 km2) (or 0.11%) is water.

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

The township contains these three cemeteries: Locust Grove, Mount Catherine and Randolph.