- AO stands for (USN Rating) Aviation Ordnanceman
- AO stands for Aaron Owens (streetball player)
- AO stands for Abdominal Obesity
- AO stands for Abgabenordnung (German tax regulations)
- AO stands for Abnormal Occurrence
- AO stands for Abort Output (TELNET protocol)
- AO stands for Academy of Osseointegration
- AO stands for Access Opening
- AO stands for Access Ordering
- AO stands for Accommodation Officer
- AO stands for Accompanying Object
- AO stands for Account Of
- AO stands for Account Owner
- A/O stands for Accounting Only
- AO stands for Accounts Office
- AO stands for Accredited Organization