OES can stand for:
- Bureau of Oceans and International Environmental and Scientific Affairs
- Old East Slavic language
- Old English Sheepdog - a breed of herding dog often kept as a pet
- Open Enterprise Server - Novell's amalgam of NetWare and Linux
- Order of the Eastern Star - a fraternal organisation
- Oregon Episcopal School - an independent, PreK-12 college-preparatory school in Portland, Oregon
- Office of Emergency Services - a governmental agency in charge of emergency & disaster planning and management
- Occupational Employment Statistics - The Occupational Employment Statistics (OES) program produces employment and wage estimates for over 800 occupations
- Open EMS Suite By Nokia Siemens Networks - A management software platform by Nokia Siemens Networks
- Optical Emissions Spectrometer - Optical Emissions Spectrometer - an instrument for testing chemical composition of metals
- O - the plural for the name of the letter "O", 'oes'
- Ordo Equitum Solis - French/Italian alternative music band