R4

R4, or R-4 may refer to:

In fiction:
*An abbreviation for R4-P17 or R4-G9 in the "Star Wars" universe

In the media:
*, a racing game for Sony PlayStation developed by Namco
* [http://games.softpedia.com/get/Freeware-Games/R4-Rocketman.shtml R4 (Rocketman)] is the sequel to R3 (computer game)
*An abbreviation for BBC Radio 4, a British radio station

In the military:
* R4 assault rifle, a South African assault rifle
* Bisnovat R-4, a Soviet missile
* Caudron R.4, a French World War I reconnaissance aircraft
* Plan R 4, the World War II British plan for an invasion of the neutral state of Norway in April 1940
* USS R-4 (SS-81), a submarine of U.S. Navy

In science and technology:
* R4 nuclear reactor, the fourth nuclear reactor built in Sweden
* , a risk phrase in chemistry
* Exotic R⁴
* an abbreviation for DVD region code 4
*R4DS, a storage device for the Nintendo DS

In transportation:
* McRae R4, a rally car designed in part by Colin McRae
* R4 ring road in Ghent, Belgium
* R4 (New York City Subway car)
* R4 (SEPTA) line of SEPTA Regional Rail (succeeded by the R5 and R8 lines) in Philadelphia, Pennsylvania
* Expressway R4, an expressway in Czech Republic
* Motorroad R4 (Slovakia)
* Audi R4, a small sports car speculated to be made sometime in the near future
* Renault 4 car
* Sikorsky R-4, the world's first mass produced helicopter
* Suzuki GSX-R/4, a concept car made by Suzuki in 2001