F18, F-18 or F.XVIII may refer to:
Transportation and military McDonnell Douglas F/A-18 Hornet, an American all-weather carrier-capable multirole fighter jet Boeing F/A-18E/F Super Hornet, a more advanced derivative of the F/A-18 Hornet F-18 (Michigan county highway), a road in the United States Fokker F.XVIII, a 1932 Dutch airliner HMS Zulu (F18), a 1937 British Royal Navy Tribal-class destroyer , an Italian Regia Marina (Royal Navy) submarine in commission from 1917 to 1929
Other uses Fluorine-18 (F-18), an unstable isotope of fluorine Slip F-18, fictional anchorage for the houseboat in the novel series starting with The Deep Blue Good-by Formula 18, a class of catamaran F18, a block in chapter V of ICD-10 for "Mental and behavioural disorders due to use of volatile solvents"