- C3 stands for Propane
- C3 stands for Colorectal Cancer Coalition (Alexandria, Virginia)
- C3 stands for Command, Control, and Communications (US DoD)
- C3 stands for College, Career, and Civic Life (education)
- C3 stands for Composition 3 (explosive)
- C3 stands for Consultation, Command and Control (NATO)
- C3 stands for Capability 3
- C3 stands for Communicatie Centrum Chemie (Dutch: Chemistry Communication Center; Netherlands)
- C3 stands for Clarity 3 (Everquest game)
- C3 stands for Cambridge Community Church
- C3 stands for Consultation, Command & Control
- C3 stands for Community Centred Conservation (UK)
- C3 stands for Schedule III Controlled Substance (USA)
- C3 stands for Career Captains Course (US Army)
- C3 stands for Ceramic Cased Capacitor
- C3 stands for CPU State 3 (normal sleep mode, computing)
C3