Nachusa Township is located in Lee County, Illinois. As of the 2010 census, its population was 493 and it contained 204 housing units. Nachusa Township was formed from China Township on February 8, 1872. It contains the census-designated place of Nachusa.
According to the 2010 census, the township has a total area of , of which (or 99.97%) is land and (or 0.03%) is water.