R4, R04, R.4, R-4, or R/4 may refer to:
Military Aircraft Caudron R.4, World War I French reconnaissance aircraft, first flown in 1915 Curtiss R-4, air ambulance version of the American Curtiss Model R utility aircraft, first flown in 1915 Sikorsky R-4, American helicopter, first flown in 1942
Ships , Royal Canadian Navy destroyer , U.S. Navy submarine
Weapons R4 assault rifle, produced by South African manufacturer Vektor Remington R4 carbine, assault rifle used by the Philippine Marine Corps Bisnovat R-4, Soviet missile
Other military Plan R 4, the World War II British plan for an invasion of the neutral state of Norway in April 1940
Science R4, designation of risk phrase "Forms very sensitive explosive metallic compounds" R4 nuclear reactor, the fourth nuclear reactor built in Sweden Exotic R4, in mathematics, a differentiable manifold
Transportation Cars R4, abbreviation for rear-engine, four-wheel drive layout R4, a sub-class of Group R rally cars Jaguar R4, Jaguar Racing's car for the 2003 Formula One season McRae R4, a rally car designed in part by Colin McRae Renault R4, alternative name for the Renault 4 Suzuki GSX-R/4, a concept car made by Suzuki in 2001
Roads R4 ring road in Ghent, Belgium R4 expressway (Czech Republic) R4 expressway (Slovakia) R-4 motorway (Spain) R4 road (Zimbabwe), a road connecting Harare and Nyamapanda Radial Road 4 or R-4, an arterial road of Manila, Philippines
Other transportation R4 (Canberra), a bus route in Canberra, Australia R4 (New York City Subway car) R4 (RER Vaud), an S-Bahn line in the canton of Vaud R4 (Rodalies de Catalunya), a commuter rail line in Barcelona, Catalonia, Spain R4 41st Avenue RapidBus, an express bus service in Vancouver, BC, Canada
Video games R4: Ridge Racer Type 4, a racing game for Sony PlayStation, developed by Namco Rush Rush Rally Racing, a racing game for Sega Dreamcast, developed by Senile Team R4 cartridge, a Nintendo DS flash cartridge
Other uses BBC Radio 4 the premier BBC speech radio station R4, a building in the Norwegian Government quarter (Norw. Regjeringskvartalet) Region 4, the DVD region code for most of Mexico, Central America, South America, Australia, New Zealand, Oceania
See also 4R (disambiguation)