Centralia Township is located in Marion County, Illinois. As of the 2010 census, its population was 15,042 and it contained 7,360 housing units.
Centralia township (T1N R1E) is centered at 38ð31'N 89ð5'W (38.517, -89.087). The city of Centralia is located in the western part of the township. The township is traversed by U.S. Route 51 (north-south) and by State Route 161 (east-west). According to the 2010 census, the township has a total area of , of which (or 97.01%) is land and (or 2.99%) is water.