ISI may stand for:
- Ice Skating International
- Indian Standards Institute
- Indian Statistical Institute
- Information Sciences Institute (USC)
- Information Security Institute
- Information Sharing Initiative (US FBI)
- Information Society Initiative
- Innovative Solutions International
- Institut Supérieur d'Informatique
- Institute for Scientific Information
- Integrated Services Internet
- Inter-Services Intelligence (Pakistan)
- International Statistical Institute
- International Students Institute (Japan)
- Iron and Steel Institute