- C4 stands for Channel 4 (UK Terrestrial Television)
- C4 stands for Carrera 4 (Porsche 911 model)
- C4 stands for Butane
- C4 stands for Middle C (piano keyboard)
- C4 stands for Command, Control, Communications, and Computers (US DoD)
- C4 stands for Composition 4 (explosive)
- C4 stands for Combat Casualty Care Course
- C4 stands for Schedule IV Controlled Substance (USA)
- C4 stands for C-4 Composition 4 (explosive)
- C4 stands for Chaos Computer Club Cologne (German computer club in Cologne member of the CCC family)
- C4 stands for Center for Clouds, Chemistry and Climate
- C4 stands for Fourth-Generation Corvette (Chevrolet)
- C4 stands for Trident I Missile Controlled Collapse Chip Connect
- C4 stands for Controlled Collapsed Chip Connection
- C4 stands for Call Centre Consulting Connection (Canada)
- C4 stands for Central CONUS Control Center (GPS)
- C-4 stands for Colonial Coin Collectors Club
- C4 stands for Care, Competence, Control and Communications (Teksystems project management methodology)
C-4