F18, F-18 or F.XVIII may refer to:

• F/A-18 Hornet, a 1978 American all-weather carrier-capable strike fighter jet
• F-18 (Michigan county highway)
• Fokker F.XVIII, a 1932 Dutch airliner
• HMS Zulu (F18), a 1937 British Royal Navy Tribal-class destroyer
• Formula 18 Catamaran
• Fluorine-18, an unstable isotope of fluorine
• F-18, Docking Slip for the "Busted Flush"

The McDonnell Douglas F/A-18 Hornet is a twin-engine supersonic, all-weather carrier-capable multirole combat jet, designed as both a fighter and attack aircraft (hence the F/A designation). Designed by McDonnell Douglas (now Boeing) and Northrop, the F/A-18 was derived from the latter's YF-17 in the 1970s for use by the United States Navy and Marine Corps. The Hornet is also used by the air forces of several other nations and, since 1986, by the U.S. Navy's Flight Demonstration Squadron, the Blue Angels.