C class submarine of the United States Navy USS Philadelphia (C-4), a protected cruiser of the United States Navy Vehicle components Ford C4 transmission, an automatic transmission Menasco C4, a 1930s 4-cylinder, air-cooled, in-line, inverted, aero-engine Weapons C-4 (explosive), a type of plastic explosive Hafdasa C-4, an Argentine submachine gun Other uses C4, a variation of Command and control, meaning "Command, Control, Communications and Computers" C4, the monogram of Christian IV of Denmark, used in the city arms of Kristianstad, Sweden since 1622 C4 Extreme, a sports nutrition supplement product line by Cellucor See also 4C (disambiguation) CCCC (disambiguation) CIV (disambiguation)