CGI
- CGI Aero
- CGI Inc.
- CGI.pm
- California Graduate Institute
- Cape Girardeau Regional Airport
- Catholic Guides of Ireland
- Cell Global Identity
- Chulabhorn Graduate Institute
- Clinical global impression
- Clinton Global Initiative
- Coast Guard Intelligence
- Cognitively Guided Instruction
- Commission for the Management and Application of Geoscience Information
- Common Gateway Interface
- Compacted graphite iron
- Compagnie Générale Immobiliere
- Computer-generated imagery
- Consultative Group on Indonesia
- Corrugated galvanised iron
- CpG islands
- Cuerpo Guardia de Infantería
- General Commissariat of Information
- Graphical Kernel System
- National Police Corps of Spain