ATG
- ATG Stores
- Advanced Technology Group (Apple)
- Advanced Technology Group (Novell)
- Alaska Territorial Guard
- Alternative Tourism Group
- Ambassador Theatre Group
- Ankara Tren Garı
- Anti Tank Guitar
- Anti-tank warfare
- Anti-thymocyte globulin
- Antigua and Barbuda
- Art Technology Group
- Art Theatre Guild
- Auction Technology Group
- Autophagy
- Aviation Technology Group
- Night vision device