South Harrison Township is one of twenty current townships in Boone County, Arkansas, USA.

Although the township includes a significant portion of the city of Harrison, it also encompasses rural areas.

Boundary lines may have been different between the former single Harrison Township and the two modern day townships.

According to the United States Census Bureau, South Harrison Township covers an area of 27.175 square miles (70.38 km2); 27.101 square miles (70.19 km2) of land and 0.074 square miles (0.19 km2) of water.

The population history includes the population of that portion of the city of Harrison which is included within the boundaries of this township.