Fox Township occupies the 6 mile square on the western edge of Kendall County, Illinois. As of the 2010 census, its population was 1,675 and it contained 619 housing units. The township was named after the Fox River, which in turn was likely named after the Fox Tribe of southeastern Wisconsin.
According to the 2010 census, the township has a total area of 36.64 square miles (94.9 km2), of which 36.17 square miles (93.7 km2) (or 98.72%) is land and 0.47 square miles (1.2 km2) (or 1.28%) is water. It includes the villages of Millbrook and Millington.