| Acronym | Definition |
|---|
| ESO | European Southern Observatory |
| ESO | European Organisation for Astronomical Research in the Southern Hemisphere |
| ESO | Ether Saga Online (gaming) |
| ESO | Enseñanza Secundaria Obligatoria (Spain Eeducational system) |
| ESO | European School of Oncology |
| ESO | Executive Stock Option |
| ESO | Ensemble Studios Online |
| ESO | Equipment Smarter than Operator |
| ESO | Environment Society of Oman |
| ESO | Extended Sexual Orgasm |
| ESO | Ecord Science Operator |
| ESO | Electrical Safety Office |
| ESO | External Security Organization (Hezbollah) |
| ESO | Equipment Superior to Operator |
| ESO | European Standardisation Organisation |
| ESO | Extended Security Option |
| ESO | Environmental Science Officer |
| ESO | Ecological Services Outsourcing (Italy) |
| ESO | East Side Oakland (California) |
| ESO | Explosives Safety Officer |
| ESO | Enterprise Service Optimization |
| ESO | Electronics Supply Office |
| ESO | Enligt Senare Order (Swedish: until further orders) |
| ESO | Emergency Security Option(s) |
| ESO | Emergency Service Override |
| ESO | European Settlements Office (banking) |
| ESO | Estimated Sign Off |
| ESO | Emergency Support Office |
| ESO | Engine Shutdown Override |
| ESO | Expanded Service Option (tape format for packaging software upgrades applied to IBM mainframe systems) |
| ESO | Engage Standard Order |
| ESO | Electronic Supply Officer |
| ESO | Equal Selection Opportunities |
| ESO | External Signaling Option |
| ESO | Environmental Services Operations |
| ESO | Evil Shop Owner |
| ESO | East Side Office |
| ESO | Electronic Sales Order |
| ESO | English Symphony Orchestra |
| ESO | Edmonton Symphony Orchestra (Canada) |
| ESO | Educación Secundaria Obligatoria (Spain: compulsory secondary education) |
| ESO | Educational Services Office(r) |
| ESO | Elgin Symphony Orchestra (Elgin, IL) |
| ESO | Emergency Service Operations |
| ESO | Employee Stock Option |