ISR
- ISR (1900)
- ISR International School on the Rhine
- ISR Racing
- In-Service Register
- In-situ recovery
- Incoherent scatter radar
- Indiana Southwestern Railway
- Information Systems Research
- Injection site reaction
- Institute for Strategy and Reconciliation
- Institutional and Scientific Relations
- Intelligence, surveillance and reconnaissance
- International Search Report
- International Socialist Review (disambiguation)
- International Star Registry
- International Statistical Review
- International Studies Review
- Interrupt service routine
- Intersecting Storage Rings
- Inuvialuit Settlement Region
- Ipoh-KL Sentral Route
- Israel
- Israel Studies Review
- Israir
- Italian Social Republic
- Joint Functional Component Command for Intelligence, Surveillance and Reconnaissance
- Plant-induced systemic resistance