IRF
- Immediate Response Force
- Impulse response function
- Inertial reference frame
- Information Retrieval Facility
- Initial Reaction Force
- Institute of Space Physics (Sweden)
- Intelligent Resilient Framework
- Interferon Regulatory Factor
- International Rabbinic Fellowship
- International Rafting Federation
- International Ranger Federation
- International Rectifier
- International Ringette Federation
- International Rogaining Federation
- Islamic Research Foundation