Olive Township is located in Madison County, Illinois, in the United States. As of the 2010 census, its population was 1,785 and it contained 842 housing units.
Olive Township was organized in 1876. Abel Olive was an early settler.
According to the 2010 census, the township has a total area of 31.52 square miles (81.6 km2), of which 31.19 square miles (80.8 km2) (or 98.95%) is land and 0.33 square miles (0.85 km2) (or 1.05%) is water.