A18 or A-18 is a three-character acronym that may refer to:
  • A18 road (disambiguation), in several countries
  • A-18 Shrike, a Curtiss Model 76A twin radial engine monoplane service test aircraft of the mid-1930s
  • Aero A.18, a Czech fighter aircraft built in the 1920s
  • Arrows A18, a Formula One car
  • British NVC community A18 (Ranunculus fluitans community), a plant community
  • Cunninghamella A18, a fungus strain
  • A18, one of the Encyclopaedia of Chess Openings codes for the English Opening in chess
  • Subfamily A18, a rhodopsin-like receptors subfamily
  • F/A-18 Hornet, an all-weather carrier-based strike fighter designed to fill the roles of fighter aircraft and attack aircraft