CIR
- Arctic Circle Air
- CIR (gene)
- CIR Group
- Cairo Regional Airport
- Campionato Italiano Rally
- Carrier-to-interference ratio
- Center for Individual Rights
- Center for Investigative Reporting
- Central ischaemic response
- Christian Initiative Romero
- Christmas Island Resort
- Circinus
- Color infrared
- Combustion Integrated Rack
- Commission Internationale de Ravitaillement
- Commissioner of Internal Revenue
- Committed information rate
- Committee on International Relations (University of Chicago)
- Comprehensive Immigration Reform Act of 2006
- Consumer IR
- Convention of Republican Institutions
- Coordinator for International Relations
- Corotating interaction region
- Cosmetic Ingredient Review
- Cox–Ingersoll–Ross model
- Cyber and Information Domain Service
- United States House Committee on Foreign Affairs