IIO
IIO or Iio may refer to:
- iiO, an American dance music group
- Iio (surname), in Japan
- Imperial Inspectorate Organization, or its successor the Islamic Inspectorate Organization in Iran
- Independent Investigations Office, a police oversight agency in British Columbia, Canada
- Italian Instabile Orchestra, an experimental big band
- Information Integration Officers, of the U.S. Air Force; see Aircrew Badge
- Diminished supertonic triad (iio), a borrowed chord
- Linux Industrial I/O subsystem