IES
- IES Ltd
- Illuminating Engineering Society
- Indian Economic Service
- Indian Education Service
- Indian Engineering Services
- Indrema Entertainment System
- Institute for Environment and Sustainability
- Institute for the International Education of Students
- Institute of Education Sciences
- Institution of Environmental Sciences
- Integrated Electrical Services
- Integrated Encryption Scheme
- International Enterprise Singapore
- Internationella Engelska Skolan
- Intertemporal elasticity of substitution
- Intuitive eating
- Israel Exploration Society
- Sixth generation of video game consoles