Oto is a city in Woodbury County, Iowa, United States. It is part of the Sioux City, IA–NE–SD Metropolitan Statistical Area. The population was 72 at the time of the 2020 census. Oto is located at 42°17′1″N 95°53′39″W / 42.28361°N 95.89417°W. It is situated near the Little Sioux River.