F4

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

Aircraft

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

F₄ (mathematics), an exceptional Lie group, or its Lie algebra ${\mathfrak {f}}_{4}$
⁠ $\mathbb {F} _{4}$ ⁠, the field with four elements
F₄, Fermat number

F4 (Istanbul Metro), a funicular railway in Istanbul Turkey
Cross Harbour ferry service, or Cross Harbour ferry services (2017–2020), Sydney, Australia
Pyrmont Bay ferry service, or Pyrmont Bay ferry services, Sydney, Australia
Albarka Air (IATA code), a Nigerian airline
Front-engine, four-wheel-drive layout, in automotive design
Italian submarine F4, an Italian Regia Marina (Royal Navy) submarine in commission from 1917 to 1919
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, an SLR camera
F4, a tornado intensity rating on the Fujita scale
F4, an electrode site according to the 10–20 system (EEG)
F4 visa, a visa used for Korean adoptees to gain South Korean citizenship