Polk Township is one of ten townships in Marshall County, Indiana, United States. As of the 2020 census, its population was 2,781 (down from 2,824 at 2010) and it contained 1,170 housing units.
Polk Township was organized on March 4, 1845. The date of the township's organization coincided with the inauguration of James K. Polk, hence the name.
The Polk Township District No. 2 School was listed on the National Register of Historic Places in 2013.
According to the 2010 census, the township has a total area of , of which (or 99.64%) is land and (or 0.38%) is water.
The township contains Barber Cemetery Blissville Cemetery and Tyner Cemetery.