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.

Fairfield Township was founded in 1844.

[5] The Maria and Franklin Wiltrout Polygonal Barn was added to the National Register of Historic Places in 1993.

[6] 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.