Oto may refer to:
- The Otoe tribe (also spelled Oto), a Native American people
- The Oto Reservation was located in southeastern Nebraska
- Oto, Iowa, a city in the United States
- Ōtō, Fukuoka, a town in Japan
- Otorohanga, a town in New Zealand, which is commonly abbreviated to 'Oto'
- Oto (album), the third album by Fluke, released in 1995
- Otocinclus, a genus of armored catfishes commonly kept in an aquarium
- Oto Melara, an Italian defense company, formerly known as Odero Terni Orlando
- Nataniela Oto, Japanese rugby player
- Seibi Oto, a fictional character
- Otomian languages (ISO 639-2 code)
OTO may also stand for:
- O.T.O., the abbreviation of Ordo Templi Orientis, which can refer to one of several Thelemic fraternal organizations:
- Ordo Templi Orientis - an international fraternal and religious organization founded at the beginning of the 20th century
- Ordo Templi Orientis (Typhonian) - a magical organisation based in Great Britain
- Osu! Tatakae! Ouendan, a popular Japanese rhythm game for the Nintendo DS