F4, F.IV, F04, F 4, F.4 or F-4 may refer to:

• Flanders F.4, a 1910s British experimental military two-seat monoplane aircraft
• Martinsyde F.4 Buzzard, a British World War I fighter version of the Martinsyde Buzzard biplane
• Fokker F.IV, a 1921 Dutch airliner
• Caproni Vizzola F.4, an Italian prototype fighter of 1939
• Lockheed F-4 Lightning, a reconnaissance variant of the Lockheed P-38 Lightning World War 2 fighter
• Fleetwings Sea Bird, a variant of which was the F-4
• A number of aircraft that first entered service with the U.S. Navy:
  • Curtiss F4C, a 1920s version of the Naval Aircraft Factory TS biplane fighter
  • Boeing F4B, a 1930s version of the Boeing P-12 biplane fighter
  • Grumman F4F Wildcat, a carrier-based fighter aircraft in World War 2
  • Vought F4U Corsair, a World War 2 fighter
  • Douglas F4D Skyray, a carrier-based fighter/interceptor, first flight 1951
  • McDonnell Douglas F-4 Phantom II, a supersonic fighter-bomber, first flight 1958

• F4, or Flower 4, the four handsome boys appearing in Japanese manga Boys Over Flowers
• F4 (band), Taiwanese boy band
• F4 Thailand, a Thai television series
• F₄, Middle F (musical note)
• Fantastic Four, fictional superhero team

• Faugère's F4 algorithm in computer algebra
• F4, a function key on a computer keyboard
• f4transkript, a transcription software
• Samsung Galaxy F04, an Android-based smartphone manufactured by Samsung Electronics

• F₄ (mathematics), the name of a Lie group and also its Lie algebra f₄
• Finite field § Field with four elements
• F₄, Fermat number

• F4 (classification), a wheelchair sport classification
• Formula 4, a class of car racing
• f4, designates a square in Algebraic notation (chess)
• 1. f4, or Bird's opening, an opening move in chess

• F4 (Istanbul Metro), a funicular railway in Istanbul Turkey
• F4 Cross Harbour, or Cross Harbour ferry services (2017–2020), Sydney, Australia
• F4 Pyrmont Bay, or Pyrmont Bay ferry services, Sydney, Australia
• Albarka Air (IATA code), a Nigerian airline
• Front-engine, four-wheel-drive layout, in automotive design
• MV Agusta F4 series, a series of motorcycles
• USS F-4, a U.S. Navy submarine that sank near Honolulu harbor in 1915
• LNER Class F4, a class of British steam locomotives

• F4, a paper size
• F 4 Frösön, a former Swedish Air Force wing
• f/4, an f-number of an optical system such as a camera lens
• F-4 Object, or Rákosi bunker, a formerly secret nuclear shelter in Budapest, Hungary
• Form F-4, an American form used to register securities
• Nikon F4, a camera
• F4, a tornado intensity rating on the Fujita scale
• F4, an electrode site according to the 10–20 system (EEG)

• 4F (disambiguation)
• Four Fs (disambiguation)