| Acronym | Definition |
|---|
| SIU | Southern Illinois University |
| SIU | Special Investigations Unit |
| SIU | Suck It Up! |
| SIU | Seafarers International Union |
| SIU | Source Interface Unit |
| SIU | Station Interface Unit |
| SIU | Special Investigative Unit |
| SIU | School Improvement Unit (various locations) |
| SIU | Société Internationale d'Urologie (French: International Society of Urology) |
| SIU | Schiller International University |
| SIU | Salem International University |
| SIU | Significant Industrial User |
| SIU | Sapporo International University (Japan) |
| SIU | System Interface Unit |
| SIU | Senter for internasjonalisering av høyere utdanning (Centre for International University Cooperation; Norway) |
| SIU | Societá Italiana di Urologia |
| SIU | Signal Interface Unit |
| SIU | Senter for Internasjonalt Universitetssamarbeid (Norwegian: Centre for International University Cooperation) |
| SIU | Serial Interface Unit |
| SIU | Système Intra-Utérin (French: Intrauterine System) |
| SIU | System Integration Unit |
| SIU | Southern Insurance Underwriters, Inc. (Georgia and Florida) |
| SIU | Sensitive Investigative Unit |
| SIU | Sets In Use (TV) |
| SIU | Service Informatique Universitaire (French: University Computing Services; University of Namur; Belgium) |
| SIU | Scheduling Information Unsolicited (health care) |
| SIU | Simulation Interface Unit (US DoD) |
| SIU | Société d'Imagerie Ultrasonore (French: Ultrasonic Imaging Society) |
| SIU | Sudan International University (Khartoum, Sudan; est. 1990) |
| SIU | Storage Interface Unit |
| SIU | Sinyal Isleme, Iletisim Ve Uygulamalari Kurultayi (Turkish) |
| SIU | Slide in Unit |
| SIU | Secondary Index Utility |
| SIU | Subsystem Interface Unit |
| SIU | Sector Intelligence Unit (US Border Patrol) |
| SIU | Special Investigative University (Colorado Springs, CO) |
| SIU | Synchronization Interval Unit |