Ios or IOS may refer to:
- Ios (Ίος), a municipality and island in the Thira (Θήρα) regional unit, South Aegean region, Greece.
- Apple iOS, a mobile operating system.
- Cisco IOS, a proprietary embedded operating system for networking devices that cannot be used with OSM data.
- IOS (Wii), a discontinued proprietary operating system for game consoles that cannot be used with OSM data.