| Acronym | Definition |
|---|
| MSSI | Medical Staffing Solutions, Inc. (various locations) |
| MSSI | Materials and Surface Science Institute (University of Limerick; Ireland) |
| MSSI | Mexican Social Security Institute (est. 1943) |
| MSSI | Mont Saint-Sauveur International (French; Canadian ski resort company) |
| MSSI | Master of Science of Strategic Intelligence |
| MSSI | Ministry of Small Scale Industries (India) |
| MSSI | Management Systems Services, Inc. |
| MSSI | Microsoft Shared Source Initiative (Microsoft Corporation) |
| MSSI | Model State Statute Initiative |
| MSSI | Measuring Stability and Security in Iraq (US DoD documentation) |