Fairfield Township is one of fifteen townships in DeKalb County, Indiana. As of the 2020 census, its population was 1,367, representing a tiny decline from 1,368 at the 2010 census,[4] and it contained 661 housing units.
According to the 2010 census, the township has a total area of 35.98 square miles (93.2 km2), of which 35.66 square miles (92.4 km2) (or 99.11%) is land and 0.31 square miles (0.80 km2) (or 0.86%) is water.[4] Indian Lake, Lower Story Lake and Upper Story Lake are in this township.