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

The African American entrepreneur and publisher of the Iowa Bystander John Lay Thompson was born on his family's farm in the township in 1869.

[1][2] Grand River Township covers an area of 35.76 square miles (92.61 square kilometers); of this, 0.07 square miles (0.18 square kilometers) or 0.19 percent is water.

The streams of South Elk Creek and West Elk Creek run through this township.

The township contains three cemeteries: Millsap, Oak Hill and Old Funk.