E4

E4, E.IV or E-4 may refer to:

Entertainment

E4 Series Shinkansen, a Japanese high-speed train
CNW Class E-4, a 4-6-4 steam locomotive of the Chicago & Northwestern Railway
EMC E4, a diesel locomotive
LB&SCR E4 class, a steam locomotive of the London, Brighton & South Coast Railway
LNER E4 Class, a 2-4-0 steam locomotive built by the Great Eastern Railway and operated by the LNER

Boeing E-4, a U.S. military flying command post
Fokker E.IV, a 1915 German fighter aircraft
E4, the fourth enlisted rank in the Military of the United States, including:
- Petty officer third class in the United States Navy and United States Coast Guard
- Senior airman in the United States Air Force (Sergeant until 1976)
- Specialist (rank) in the United States Army (if the soldier is not a non-commissioned officer)
- Corporal in the United States Army and United States Marine Corps (if the soldier is a non-commissioned officer)

E4-isoprostane, a type of isoprostane
Leukotriene E4, a naturally produced eicosanoid lipid mediator
E-4 process, an obsolete development process associated with photographic transparency film
Honda E4, a predecessor of Honda's ASIMO robot
RCS-4, a synthetic cannabinoid sold as "E-4"
E4 or E₄, an old name for the exceptional group F₄
Estetrol, an estrogen

Big Four (Western Europe), sometimes called 'E4', a group of powerful countries in Europe
E4, a postcode district in the E postcode area
King's Pawn Game, or 1. e4, a chess opening move
E4 grade, a grade of difficulty in rock climbing
E4 or E₄, musical notation indicating the E above Middle C