South Rock Island Township is located in Rock Island County, Illinois. As of the 2010 census, its population was 18,407 and it contained 8,951 housing units. South Rock Island Township formed from Rock Island Township on March 1, 1878.
According to the 2010 census, the township has a total area of , of which (or 93.18%) is land and (or 6.82%) is water.