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- Oak Township, Mills County
- Oak Dale Township, Howard County
- Oakfield Township, Audubon County
- Oakland Township, Franklin County
- Oakland Township, Louisa County
- Ocheyedan Township, Osceola County
- Ohio Township, Madison County
- Okoboji Township, Dickinson County
- Olive Township, Clinton County
- Omega Township, O'Brien County
- Oneida Township, Delaware County
- Oneida Township, Tama County
- Oran Township, Fayette County
- Orange Township, Black Hawk County
- Orange Township, Clinton County
- Orange Township, Guthrie County
- Oregon Township, Washington County
- Orient Township, Adair County
- Orleans Township, Winneshiek County
- Orono Township, Muscatine County
- Orthel Township, Hancock County
- Osage Township, Mitchell County
- Osceola Township, Clarke County
- Osceola Township, Franklin County
- Otho Township, Webster County
- Oto Township, Woodbury County
- Otranto Township, Mitchell County
- Otter Township, Warren County
- Otter Creek Township, Crawford County
- Otter Creek Township, Jackson County
- Otter Creek Township, Linn County
- Otter Creek Township, Lucas County
- Otter Creek Township, Tama County
- Owen Township, Cerro Gordo County
- Oxford Township, Johnson County
- Oxford Township, Jones County
Read more about this topic: List Of Iowa Townships