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.

• Decatur City

• Long Creek Township (north)
• Franklin Township (northeast)
• Center Township (east)
• Eden Township (southeast)
• Burrell Township (south)
• Bloomington Township (southwest)
• Grand River Township (west)
• Richland Township (northwest)

The township contains six cemeteries: Cash, Decatur City, Palenstine, Shy, Waller and Woodmansee.

• Interstate 35

• U.S. Board on Geographic Names (GNIS)
• United States Census Bureau cartographic boundary files

• US-Counties.com
• City-Data.com