GSI
- GS (disambiguation)
- GS-1 (disambiguation)
- GS-I
- GSI Helmholtz Centre for Heavy Ion Research
- GSIS (disambiguation)
- GSL (disambiguation)
- Gemological Science International
- Geographical Society of Ireland
- Geological Society of India
- Geological Strength Index
- Geological Survey of India
- Geological Survey of Ireland
- Geophysical Service Incorporated
- Geospatial Information Authority of Japan
- Global Security Initiative
- Gonadosomatic Index
- Government Secure Intranet
- Grand-Santi Airport
- Great Sea Interconnector
- Grid Security Infrastructure
- Guangzhou Shipyard International
- Gustav Stresemann Institute
- Institutional Security Cabinet
- Systems Integrator
- Teaching fellow