| SIU | International Society of Urology 
| Others |
| SIU | Saab Information Unit
| Others |
| SIU | Scheduling Information Unsolicited
| Others |
| SIU | Seafarers International Union
| Others |
| SIU | Seiko Instruments USA, Inc.
| Others |
| SIU | Sensor Interface Unit
| Others |
| SIU | Serious Incident Unit
| Others |
| SIU | Shake It Up
| Others |
| SIU | Shelf Interface Unit
| Others |
| SIU | Shut It Up
| Others |
| SIU | Signal Interface Unit
| Others |
| SIU | Significant Industrial User
| Others |
| SIU | Simulation Interface Unit
| Others |
| SIU | Skin Installer Ultimate
| Others |
| SIU | Slave In Utero
| Others |
| SIU | Source Interface Unit
| Others |
| SIU | Southern Illinois University
| Others |
| SIU | Special Infiltration Unit
| Others |
| SIU | Special Investigation Unit
| Others |
| SIU | Special Investigations Unit
| Others |
| SIU | Special Investigative Unit
| Others |
| SIU | Special Investigative Units
| Others |
| SIU | Specialized Intervention Unit
| Others |
| SIU | Station Interface Unit
| Others |
| SIU | Stimulus Isolation Unit
| Others |
| SIU | Supplementary Indicators to Unemployment
| Others |
| SIU | System Identification Utility
| Others |
| SIU | System Interface Unit
| Others |