Fos
- FOS Open Scouting
- FOSL1
- FOSL2
- Fabric OS
- Factor of safety
- Faint Object Spectrograph
- Feature-oriented scanning
- Fields of Science and Technology
- Financial Ombudsman Service
- Financial Ombudsman Service (Australia)
- Florida Ornithological Society
- Flowers of sulfur
- Flowers of sulfur tests
- Forrest Airport
- Fortress of Solitude
- Forward Operating Site
- Fos (EP)
- Fos Williams
- Fos, Haute-Garonne
- Fos, Hérault
- Fos-sur-Mer
- FosB
- Freedom of speech
- French onion soup
- Fructooligosaccharide
- Future Office System
- Goodwood Festival of Speed
- Marseille-Fos Port
- Overseas territory (France)
- Peter J. Fos
- ΔFosB