•
Intercollegiate Studies Institute, a classical conservative organization focusing on college students •
Ice Skating Institute, a trade association for ice rinks •
Indian Standards Institute, former name of the national standards body of India, the Bureau of Indian Standards •
ISI mark, a product certification mark in India •
Institute for Scientific Information, part of Clarivate Analytics (formerly the Healthcare & Science business of the Thomson Reuters Corporation) •
Institute for Scientific Interchange, a theoretical scientific research centre based in Turin, Italy •
Inter-Services Intelligence, an intelligence agency of Pakistan •
International Statistical Institute, a professional association of statisticians • International Systems Institute, a scientific and educational corporation founded by
Béla H. Bánáthy •
Iron and Steel Institute, precedent organization to the Institute of Materials, Minerals and Mining •
Islamic State of Iraq, an umbrella organization of a number of Iraqi insurgency groups •
Integral Satcom Initiative, the European Technology Platform on Satellite Communications •
Independent Schools Inspectorate, responsible for the inspection of independent schools and private further education colleges in England •
Integrated Systems, Inc., a former developer of real-time operating systems •
Image Space Incorporated, an independent video game developer •
ImageSat International, an Israeli satellite imagery company
Schools and educational institutions •
Indian Statistical Institute, a public research institute and university in Baranagar, Kolkata, India • Indonesian Institute of the Arts, a collective name of arts university in Indonesia: •
Indonesian Institute of the Arts, Denpasar •
Indonesian Institute of the Arts, Surakarta •
Indonesian Institute of the Arts, Yogyakarta •
Information Sciences Institute, a research and development unit of the University of Southern California's Viterbi School of Engineering • Institute of Scientific Instrumentation, a subsidiary of the Bangladesh
University Grants Commission •
Intercollegiate Studies Institute, a non-profit educational organization •
International School Ibadan, a school located on the Campus of the University of Ibadan •
International School of Iceland, a school located in Garðabær, Iceland, a suburb of the capital city of Reykjavík •
Islamic School of Irving, in the Dallas-Fort Worth area ==Science and technology==