C5 or C-5 may refer to:

• Citroën C5, a brand of car manufactured by Citroën
• Sinclair C5, an electric moped designed by Clive Sinclair
• Corvette C5, the fifth generation of the Chevrolet Corvette sports car
• "C5", another name for the ChorusOS computer operating system
• C5 is the envelope size matching the A5 paper size
• Fifth cervical vertebra of the vertebral column, in human anatomy
• C5, or Tenor C
• C5 is the IATA code for Champlain Enterprises an airline
• C5.0, a data mining tool for discovering patterns in extensive databases
• HMS C5, a British C-class submarine of the Royal Navy
• USS C-5, a C class submarine of the United States Navy
• USS San Francisco (C-5), a protected cruiser of the United States Navy
• An inactive complement protein of the complement system. It can be split by C5-convertase into C5a, an inflammatory peptide, and C5b
• A polarised, three pole, mains voltage IEC connector
• C5, the fifth production design of the Chevrolet Corvette
• The Lockheed C-5 Galaxy is one of the largest military aircraft in the world.
• C.V, a German designation for several World War I armed reconnaissance aircraft:
  • AEG C.V
  • DFW C.V

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