Oto is a city in Woodbury County, Iowa, United States.

It is part of the Sioux City, IA–NE–SD Metropolitan Statistical Area.

According to the United States Census Bureau, the city has a total area of 0.27 square miles (0.70 km2), all land.

There were 44 housing units at an average density of 163.6 per square mile (63.2/km2).

There were 60 housing units at an average density of 222.2 per square mile (85.8/km2).

39.1% of all households were made up of individuals, and 26.1% had someone living alone who was 65 years of age or older.

The racial makeup of the city was 96.55% White, 2.76% Native American, and 0.69% from two or more races.

24.1% of all households were made up of individuals, and 14.8% had someone living alone who was 65 years of age or older.

There were 11.1% of families and 21.3% of the population living below the poverty line, including 23.6% of under eighteens and none of those over 64.