| Acronym | Definition |
|---|
| IRSI | Istituto Ricerche Sicurezza Industriale (Italian: Industrial Safety Research Institute; est. 1974; Milan, Italy) |
| IRSI | Intelligent Reasoning Systems, Inc. (software) |
| IRSI | Illinois Retirement Security Initiative (Chicago, IL) |
| IRSI | Investor Relations Services, Inc. (New Smyrna Beach, FL) |
| IRSI | Instituto de Robótica y Sistemas Inteligentes (Spanish: Institute of Robotics and Intelligent Systems; Universidad de Guadalajara; Mexico; also seen as IRIS) |
| IRSI | Institute of Regional Studies Islamabad (Pakistan) |