CSI may stand for:
- California Spine Institute
- California Steel Industries Inc.
- Canadian Securities Institute (csi.ca)
- Canadian Seed Institute
- Canadian Sugar Institute
- Cardiological Society of India
- Carrier Scale Internetworking
- Cast Stone Institute
- Causal side information
- Center for Sports Innovation (MIT)
- Center for the Study of Intelligence (CIA)
- Cetacean Society International
- Chemical shift imaging
- Chicago Systemic Initiative
- Christian Schools International
- Christian Solidarity International
- Christian Sports International
- Church of Scientology International
- Church of South India
- Coalition of Service Industries
- Collision Safety Institute
- College of Staten Island
- Combat Studies Institute (US Army)
- Combat system integration
- Command Systems, Inc
- Commercial satellite imagery
- Common software interface
- Companion of The Most Exalted Order of the Star of India
- Complex specified information
- Compton scatter imaging
- CompuServe Inc.
- Computer Sales International Inc.
- Computer Security Institute
- Computer Society of India
- Conditional symmetric instability
- Construction Specifications Institute
- Consumer Safety Inspector
- Consumer Science Index
- Convergence Solutions, Inc
- Coral Sea Islands
- CSI: Crime Scene Investigation (television series)
- Cuban Studies Institute