| Acronym | Definition |
|---|
| ATSI | Aboriginal and Torres Strait Islander (Australia) |
| ATSI | Association of TeleServices International |
| ATSI | American Technology Solutions International |
| ATSI | Advanced Technology Solutions, Inc. |
| ATSI | Advanced Technology Services, Inc. (Arizona) |
| ATSI | Association of Thai Software Industry |
| ATSI | American Transmission Systems, Inc. |
| ATSI | Anderson Trucking Service, Inc. (various locations) |
| ATSI | Association of Telemessaging Services International |
| ATSI | Asosiasi Telekomunikasi Seluler Indonesia (Association of Indonesian Cellular Operators) |
| ATSI | Alias TETRA (Terrestrial Trunked Radio) Subscriber Identity (telecommunications) |
| ATSI | Aero Transcription Service, Inc. (Baltimore, MD) |
| ATSI | Arcus Technology Services Inc |