CSO
- Bureau of Conflict and Stabilization Operations
- CCSO Nameserver
- CSO Online
- Caltech Submillimeter Observatory
- Canberra Symphony Orchestra
- Canton Symphony Orchestra
- Carbonyl sulfide
- Carmel Symphony Orchestra
- Central Statistical Office (disambiguation)
- Central Statistical Organisation
- Central Statistics Office (Ireland)
- Central Statistics Office (disambiguation)
- Central Statistics Organization
- Charleston Symphony Orchestra
- Charlotte Symphony Orchestra
- Chicago Symphony Orchestra
- Chief Scientist Office
- Chief Signal Officer
- Chief of Space Operations
- Chief scientific officer
- Chief security officer
- Chief services officer
- Chief strategy officer
- Chief sustainability officer
- Christchurch Symphony Orchestra
- Cincinnati Symphony Orchestra
- Circuito Sur de Oriente
- Civil society organization
- Coastal States Organization
- Colorado Symphony Orchestra
- Colour-separation overlay
- Columbia Symphony Orchestra
- Columbus Symphony Orchestra
- Combat systems officer
- Combined sewer
- Community Service Organization
- Community service officer
- Composante Spatiale Optique
- Compulsory stock obligation
- Computer Science Ontology
- Conference of Solidarity Support Organizations
- Counter-Strike Online
- Court security officer (disambiguation)
- Czech Statistical Office
- Magdeburg–Cochstedt Airport
- Nexon
- Police community support officer
- Sales manager