| Acronym | Definition |
|---|
| SIIS | Statewide Immunization Information System |
| SIIS | Shanghai Institute for International Studies (international relations research organization; Shanghai, China) |
| SIIS | State Industrial Insurance System (Nevada) |
| SIIS | Southwestern Insurance Information Service |
| SIIS | Subsea Instrumentation Interface Standardisation (electronics equipment protocol) |
| SIIS | Spacecraft/Instrument Interface Simulator |
| SIIS | Seikei Institute for International Studies (Seikei University; Japan) |
| SIIS | Stanford University's Institute for International Studies |