ISI

Organizations

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

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:
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

Information Sharing Index, former name of ContactPoint, a government database that held information on all children in England
Infrared Spatial Interferometer, an astronomical interferometer array of three telescopes
International Sensitivity Index, an index value used to standardize different thromboplastins for use in blood coagulation testing
Interstimulus interval, the temporal interval between the offset of one stimulus to the onset of another
Intersymbol interference, a form of distortion of a signal in which one symbol interferes with subsequent symbols
Instruction Storage Interrupt, segmentation fault of a PowerPC