556 (disambiguation)

556 is the year 556 AD.

556 may also refer to:

• 556 (number)
• 556 BC
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• 5.56mm or 5.56×45mm NATO, a common rifle cartridge
• Sig 556, a commercial variant of the Sig SG 551 rifle designed for the American civilian market
• 5-56, a popular brand of penetrating oil
• 556 dual timer, an integrated circuit
• 556, a fictional character in the Sgt. Frog series