- COMTAC (TACtical COMmunications)
- COMUSAFE (COMmander, United States Air Force In Europe)
- COMUSARCENT (COMmander, United States ARmy Forces, CENTral Command)
- COMUSCENTAF (COMmander, United States Air Force, CENTral Command)
- COMUSFLTFORCOM (COMmander, United States FLeeT FORces COMmand)
- COMUSFORAZ (COMmander, United States FORces, AZores)
- COMUSJ (COMmander, United States Forces, Japan)
- COMUSK (COMmander, United States Forces, Korea)
- COMUSLANTFLT (COMmander, United States AtLANTic FLeeT)
- COMUSMARCENT (COMmander, United States MARine Forces, CENTral Command)
- COMUSNAVCENT (COMmander, United States NAVy, CENTral Command)
- COMUSPACFLT (COMmander, United States PACific FLeeT)
- COMUSSOCJFCOM (COMmander, Special Operations Command, United States Joint Forces COMmand)
- COMVAT (Combat vehicles armament technology (US))
- COMZ (Communications zone)
- CON (Certificate of Need)
- Con. (Contra ("against"))
- CONAD (U.S. Continental Air Defense Command)
- CONAF (Conceptual Design for the Army in the field)
- conc (concentrated)
- CONCAB (CONference CABinet)
- CONCACAF (Confederation Of North, Central American and Caribbean Association Football)
- CONCAP (CONstruction CAPabilities)
- CONCERN (CONquer canCER Now)
- CONDE (condensate analysis report)
- CONDR (continuous directional log)
- Cone. (Concilium ("Council"))
- ConEd (Continuing Education)
- CONEX (Container Express)
- CONEXPLAN (CONtingency and EXercise PLAN)
- Conf. (Confessor)
- CONF (Confidential)
- CONFAD (CONcept for a Family of Army Divisions)
- Conf. Doct. (Confessor et Doctor (Breviary))
- Confeone. (Confessione ("Confession" abl. case))
- Conf. Pont. (Confessor Pontifex ("Confessor and Bishop" Breviary))
- CONG (Viet-Cong)
- CONII (Colleges Ontario Network for Industry Innovation)
- CONMEBOL (Confederación Sudamericana de Fútbol or Confederação Sul-Americana de Futebol (respectively Spanish and Portuguese for "South American Football Confederation"))
- CONN (CONNector)
- Connie (Constance)
- CONOPS (Concept of Operations)