C2 or C-2 can refer to:

• Vitamin C2, a name sometimes used for Choline.
• C2, an international standard paper size (458×648 mm), defined in ISO 216.
• Coca-Cola C2, a soft drink launched by The Coca-Cola Company in 2004.
• C2, a file transfer protocol.
• HMS C2 , a C-class submarine of the Royal Navy.
• USS C-2, a C-class submarine of the United States Navy.
• USS Charleston (C-2), a protected cruiser of the United States Navy.
• The Grumman C-2 Greyhound, a cargo aircraft of the United States Navy.
• The Citroën C2, a car produced by Citroën in 2004.
• C2, a form of plastic explosive.