The acronym IES can stand for:
- Illuminating Engineering Society of North America
- Indian Economic Service
- Indian Education Society
- Indian Engineering Service
- Institute of Education Sciences
- Institute for Environment and Sustainability of the European Commission
- Institute for the International Education of Students
- integral Ecosystem Services
- Integrated Electrical Services, Inc
- Integrated Environmental Solutions, an engineering and environmental software company
- International Euphorbia Society
- Israel Exploration Society
- Institution of Environmental Sciences
- Indian Engineering Services
- Integrated Encryption Scheme, in cryptography, a public key cryptosystem
- Internationella Engelska Skolan
- Intertemporal elasticity of substitution
- Integrated Export Systems, referred to as IES Ltd, a transportation software company