A12 or A-12 can refer to:

• The A12, a road in England from London to Great Yarmouth.
• One of three separate aircraft:
  • The A-12 Shrike, a World War II-era aircraft.
  • The Lockheed A-12 Oxcart, a prototype interceptor aircraft.
  • The A-12 Avenger II, a Cold War-era aircraft project that was cancelled prior to production.
• The A12, a German rocket during World War II, never realized.
• HMS A12, an A-class submarine of the Royal Navy.