The initialism IES may refer to: Government organizations Indian Economic Service Indian Education Service, in British India Institute for Environment and Sustainability of the European Commission Institute of Education Sciences of the U.S. Department of Education Non-profit organizations Institute for the International Education of Students Illuminating Engineering Society International Enterprise Singapore International Society of Endocrinology Israel Endocrine Society Israel Exploration Society Institution of Environmental Sciences Companies IES Ltd (Integrated Export Systems), a transportation software company Integrated Electrical Services Internationella Engelska Skolan Other Indian Engineering Services Integrated Encryption Scheme, in cryptography, a public key cryptosystem Intertemporal elasticity of substitution