| Acronym | Definition |
|---|
| USI | University of Southern Indiana |
| USI | USinternetworking, Inc. (Annapolis, MD) |
| USI | Union of Students in Ireland |
| USI | Unité de Santé Internationale (French: International Health Unity; Canada) |
| USI | User Service Information |
| USI | Universal Sim Interface |
| USI | User Specific Interface |
| USI | Usb Interface |
| USI | United Stationers, Inc. (Deerfield, IL) |
| USI | Universal Salt Iodization (WHO/UNICEF) |
| USI | Urban Systemic Initiative |
| USI | Urban School Improvement |
| USI | Universidad de Sta Isabel (Naga City, Philippines) |
| USI | User System Interface (Alcatel) |
| USI | Universal Systems, Inc. |
| USI | United Submitters International (religious group) |
| USI | Ultrasonic Systems Inc (Haverhill, MA) |
| USI | Utility Services, Inc. (subsidiary of MDU Resources Group) |
| USI | Ultrasonic Imaging |
| USI | Unresolved Safety Issue |
| USI | Unwarranted Self-Importance (Internet slang) |
| USI | Universal Swap Identifier (financial regulations) |
| USI | User Service Information (ITU-T) |
| USI | Union Sportive d'Ivry (French sports club) |
| USI | United Schools International (Indonesia) |
| USI | Universal Scanner Interface |
| USI | Unique Secondary Index |
| USI | US Interactive, Inc |
| USI | ULANA Service Interface |
| USI | Uniform Side-Information |
| USI | União de Sindicatos Independentes (Portugese: Union of Independent Trade Unions) |
| USI | Unione Sidacale Italiana (Italian: Italian Workers Union) |
| USI | Universal System Identifier (US DoD) |