IFS
- Frame (networking)
- Genesis Intelligent Front-lighting System
- Ifs, Calvados
- Indian Foreign Service
- Indian Forest Service
- Industrial and Financial Systems
- InfoPath Forms Services
- Initial Flight Screening
- Installable File System
- Institut für Sexualwissenschaft
- Institute for Fiscal Studies
- Integral field spectroscopy
- Integrated Forecast System
- Interframe spacing
- Internal Family Systems Model
- Internal field separator
- International Film Service
- International Financial Statistics
- International Foundation for Science
- International French School Singapore
- International Futures
- International Sumo Federation
- Internationale Filmschule Köln
- Irish Free State
- Islamic Foundation School
- Isoflavonoid synthase
- Iterated function system
- List of United States Navy amphibious warfare ships
- Network packet
- Norwegian Institute for Defence Studies
- University of Frankfurt Institute for Social Research