ISI or Isi may refer to:
- İsi, a village and municipality in the Masally Rayon of Azerbaijan
- ContactPoint (previously Information Sharing Index), a government database that held information on all children under 18 in England
- Ice Skating Institute, a trade association for ice rinks
- Image Space Incorporated, an Independent video game developer
- Import substitution industrialization, a trade and economic policy
- Infrared Spatial Interferometer, an astronomical interferometer array of three telescopes
- 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
- ISI mark, a product certification mark in India
Read more about ISI: World No 1 Organizations, Schools