| Acronym | Definition |
|---|
| SIO | Scripps Institution of Oceanography |
| SIO | Studentsamskipnaden i Oslo |
| SIO | Serial Input/Output |
| SIO | Senior Intelligence Officer |
| SIO | Social Investment Organization (Canada) |
| SIO | Spit It Out |
| SIO | Service Information Octet (SS7) |
| SIO | Skidaway Institute of Oceanography |
| SIO | Senior Investigation Officer (UK) |
| SIO | special information operations (US DoD) |
| SIO | serious inquiries only |
| SIO | Systems Integration Office |
| SIO | Societas Internationalis Odonatologica |
| SIO | Services in Operation |
| SIO | Standard Installation Organization |
| SIO | Status Indication Out of Alignment (SS7) |
| SIO | Simultaneous Input Output |
| SIO | Shanghai Informatization Office |
| SIO | Section Interorganisations |
| SIO | Slave Input/Output |
| SIO | Stakeholder Involvement Office |
| SIO | Student Islamic Organization (India) |
| SIO | Security and Information Operations |
| SIO | Synchronizing Intermediate Objectives |
| SIO | Scalable Input/Output Initiative (California Institute of Technology) |
| SIO | SOGS Interface Unit |
| SIO | Special Intelligence Officer |
| SIO | Sprint Integrated Office |
| SIO | Safety Interlock Override |
| SIO | Smart Input/Output (part of TEDS from IEEE standard 1451.1) |
| SIO | Supply Item Order |
| SIO | Social Improvement Organization |
| SIO | Second Institute of Oceanography (China) |
| SIO | Service Inventory Optimization (software) |
| SIO | Strategic Initiatives Overview (management) |