E4

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

Entertainment

 * E4 (TV channel), a digital television channel in the United Kingdom and Ireland
 * Every Extend Extra Extreme, a video game from Q Entertainment
 * Entertainment for All, a video game expo

Transportation

 * Aero Asia International, an airline, by IATA code

Roads

 * European route E4, a road through Finland and Sweden
 * E4 European long distance path, a European long-distance trail
 * Tōhoku Expressway, route E4 in Japan
 * E4 expressway (Pakistan)
 * South Kedah Expressway in Malaysia
 * Subic Freeport Expressway in the Philippines

Trains

 * 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

Military

 * 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)

Science and technology

 * 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

Other uses

 * 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