Tonti Township is located in Marion County, Illinois. As of the 2010 census, its population was 1,013 and it contained 430 housing units.
Tonti Township was named in honor of Henry de Tonti, an early Italian/French explorer of Illinois.
Tonti Township (T3N R2E) is centered at 38ð41'N 88ð58'W (88.691,-88.975). It is transversed northeastâÂÂsouth by Interstate Route 57 and State Route 37. Part of the Salem Reservoir (El. 166 m) is located at the southeastern part of the township. According to the 2010 census, the township has a total area of , of which (or 99.72%) is land and (or 0.28%) is water.