| Official Name: | Decatur Township |
| Settlement Type: | Township |
| Subdivision Type: | Country |
| Subdivision Type1: | State |
| Subdivision Type2: | County |
| Subdivision Name2: | Decatur |
| Area Total Km2: | 92.65 |
| Area Land Km2: | 92.3 |
| Area Water Km2: | 0.35 |
| Unit Pref: | Imperial |
| Area Total Sq Mi: | 35.77 |
| Area Land Sq Mi: | 35.64 |
| Area Water Sq Mi: | 0.14 |
| Area Water Percent: | 0.38 |
| Population As Of: | 2000 |
| Population Total: | 425 |
| Population Density Km2: | 4.6 |
| Population Density Sq Mi: | 11.9 |
| Elevation M: | 336 |
| Elevation Ft: | 1102 |
| Coordinates: | 40.7664°N -93.8369°W |
| Blank Name: | GNIS feature ID |
| Blank Info: | 0467689 |
Decatur Township is a township in Decatur County, Iowa, United States. As of the 2000 census, its population was 425.
Decatur Township covers an area of 35.77 square miles (92.65 square kilometers); of this, 0.14 square miles (0.35 square kilometers) or 0.38 percent is water. The streams of Long Creek and Marks Branch run through this township.
The township contains six cemeteries: Cash, Decatur City, Palenstine, Shy, Waller and Woodmansee.