| Abbreviation | Definition |
|---|---|
| ATRA | American Trail Running Association |
| ATRA | Arkansas Teenage Rodeo Association |
| ATRO | Association of Tenancy Relations Officers |
| ATS | Association of Theological Schools |
| ATSA | American Tornado Shelter Association |
| ATSA | Association for the Treatment of Sexual Abusers |
| ATSA | Association for Translation Studies in Africa |
| ATSA | Association of Togolese Students in America |
| ATSP | Association of Telehealth Service Professionals |
| ATSP | Association of Telemedicine Service Providers |
| ATSS | Association of Teachers of Social Studies |
| ATT | Association of Top Talents |
| ATTF | Association des Techniciens Territoriaux de France |
| ATVA | All Terrain Vehicle Association |
| ATVA | American Trauma Victims Association |
| ATWAP | Association of Table Water Association Producers |
| AUA | American Urologic Association |
| AUA | American Urological Association's |
| AUA | ARV Users Association |
| AUAAA | Adelaide University Aquatic Animal Association |