ATU
- ATU Network
- Aarne–Thompson–Uther Index
- Abstract Tribe Unique
- Administrative divisions of Moldova
- African Telecommunications Union
- Allameh Tabataba'i University
- Amalgamated Transit Union
- Antenna tuning unit
- Anti-Terrorist Unit (Liberia)
- Arkansas Tech University
- Asian Taekwondo Union
- Atlantic Technological University
- Atu
- Atu Bosenavulagi
- Atu Moli
- Atu'u
- Atu, Iran
- Autoridad de Transporte Urbano
- Finnish Rapid Deployment Force
- Lučko Anti-Terrorist Unit
- Taekwondo