IOO
| Acronym | Definition |
|---|---|
| IOO | In Our Opinion |
| IOO | Independent Owner Operator (truck driver) |
| IOO | Institut für Orgonforschung |
| IOO | Idaho Operations Office |
| IOO | Institut Ochrany Obyvatelstva (Czech: Institute of Protection of the Population; est. 1991) |
| IOO | Internet Order Online (Poland) |