OES
- Bureau of Oceans and International Environmental and Scientific Affairs
- O
- Occupational Employment Statistics
- Oes
- Office of Emergency Services
- Old East Slavic
- Old English Sheepdog
- On Every Street
- Open Enterprise Server
- Operators of essential services
- Optical Emissions Spectrometer
- Order of the Eastern Star
- Ordo Equitum Solis
- Oregon Episcopal School
- Original equipment supplier