| Acronym | Definition |
|---|
| IOS | Internetwork Operating System |
| IOS | Independent On Sunday |
| iOS | iPhone Operating System (Apple) |
| IOS | Internet Operating System |
| IOS | Institute of Ocean Sciences (Canada) |
| IOS | Instructor Operator Station |
| IOS | Institute of Sociology |
| IOS | Institute of Oceanographic Sciences |
| IOS | Is ook schitterend (Dutch band) |
| IOS | Instructor Operating Station |
| IOS | Interorganizational System |
| IOS | International Outsourcing Services |
| IOS | Internet Over Satellite |
| IOS | Input/Output Subsystem |
| IOS | Institute of Objective Studies (India) |
| IOS | International Organization for Standards |
| IOS | Interorganizational Information System |
| IOS | Integrated Observing System |
| IOS | Input/Output Supervisor |
| IOS | Institute for Optical Sciences (University of Toronto; Canada) |
| IOS | Integrated Office System |
| IOS | I'm Only Sleeping (Beatles song) |
| IOS | Ilheus, Bahia, Brazil - Eduardo Gomes (Airport Code) |
| IOS | Insurance Overload Staffing (Dallas, TX) |
| IOS | Intelligence Operations Specialist (US Federal Bureau of Investigation) |
| IOS | International Online Soccer (gaming, Half-Life modification) |
| IOS | Institute for Orgonomic Science |
| IOS | International Oak Society |
| IOS | Internet Ophthalmology Society |
| IOS | Inter-Operability Specification |
| IOS | Initial Operational System |
| IOS | International Officer School |
| IOS | Inter-Operability Standard |
| IOS | Integrated Observation System |
| IOS | Igoss Observing System |
| IOS | International Operator Services (Sprint) |
| IOS | Interim Operational Supplement |
| IOS | Indian Ocean Tracking Station (AFSCN) |
| IOS | Intranet Operating System |
| IOS | Inventory Of Service |
| IOS | Internal Order System |
| IOS | Illinois Orthopaedic Society |
| IOS | Intelligence Operations System (USMC replacement for TCO and IAS Suites) |
| IOS | Integrated Operational Services |
| IOS | Inter-Organizations Section |
| IOS | Intermediate Open System |
| IOS | Improved Oceanographic Sensor |
| IOS | Interconnected Operating System |
| IOS | Inactive, Obsolete, Surplus (jobs) |
| IOS | Individual Ordinance Summary |
| IOS | Integrated Operations Scenario |
| IOS | Initial Operating Sector |
| IOS | Internal Opportunity System (Motorola) |
| IOS | Infinity Optical Systems |
| IOS | Interim Operational System |
| IOS | Integrated Outsourcing Services GmbH (Germany) |
| IOS | Institute of Software (Chinese Academy of Sciences) |
| IOS | Issues of Substance (Canada) |
| IOS | Institute of Statisticians (est. 1948; now Royal Statistical Society; UK) |
| IoS | Index of Services (service industries; various locations) |