Decatur Township is a township in Decatur County, Iowa, United States.

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.

This article about the geography of Decatur County, Iowa is a stub.