Allen Township is one of fourteen townships in Miami County, Indiana, United States. As of the 2020 census, its population was 642 (down from 695 at 2010[3]) and it contained 258 housing units.
According to the 2010 census, the township has a total area of 21.62 square miles (56.0 km2), of which 21.51 square miles (55.7 km2) (or 99.49%) is land and 0.11 square miles (0.28 km2) (or 0.51%) is water.[3]