E1

E1, E01, E.I or E-1 may refer to:

Aircraft

 * Azcárate E-1, a Mexican sesquiplane trainer
 * Fokker E.I, a German fighter aircraft
 * Grumman E-1 Tracer, an American airborne early warning aircraft
 * Hydra Technologies E1 Gavilán, a hand-launched Mexican unmanned electronic surveillance drone
 * Junkers E.I, the Idflieg designation for the 1916 Junkers J1 monoplane
 * LVG E.I, a 1915 German two-seat monoplane
 * NFW E.I, a 1917 German monoplane fighter
 * Pfalz E.I, a Morane-Saulnier H monoplane built under licence for Germany
 * Siemens-Schuckert E.I, a 1915 German single seat monoplane
 * Standard E-1, a 1917 early American Army fighter aircraft

Automobiles

 * BMW E1, a 1991 and 1993 German electric/hybrid city car concept
 * BYD e1, a 2019–present Chinese electric city car
 * Dongfeng Fengguang E1, a 2019–present Chinese electric mini crossover
 * Haima E1, a 2020–present Chinese electric city car
 * Roewe E1, a 2012 Chinese electric city car concept later produced as the Roewe E50
 * E1, a Mazda E type piston engine
 * Switch E1, a bus Built by Switch Mobility
 * Bestune E01, a compact electric crossover

Submarines

 * HMS E1, an E-class submarine of the Royal Navy
 * USS E-1 (SS-24), a 1917 E-class submarine of the United States Navy

Roads

 * E01, Southern Expressway in Sri Lanka
 * European route E01, from Northern Ireland to Spain
 * E1 European long distance path, a long-distance hiking route from Norway to Italy
 * London Buses route E1, a transport for London contracted bus route
 * Tomei Expressway and Meishin Expressway, route E1 in Japan
 * North–South Expressway Northern Route and New Klang Valley Expressway, route E1 in Malaysia
 * E1 expressway (Philippines) (North Luzon Expressway, Subic–Clark–Tarlac Expressway, and Tarlac–Pangasinan–La Union Expressway), expressway route in the Philippines
 * E1 expressway (Pakistan)

Trains and locomotives

 * E1 Series Shinkansen, a Japanese high-speed train
 * Bavarian E I, a German steam engines locomotive model
 * EMC E1, a diesel locomotive
 * LB&SCR E1 class, an 1874 British 0-6-0 steam locomotive
 * NCC Class E1, a Northern Counties Committee Irish steam locomotive
 * NER Class E1, an 1898 class of small 0-6-0T steam locomotive
 * PRR E1, an American PRR 4-4-2 steam locomotive
 * SP&S Class E-1, a 1934 steam locomotives class

Biochemistry

 * E1 (HCV), a viral structural protein found in hepatitis C
 * E1, a unimolecular elimination mechanism in organic chemistry
 * E1-enzymes, also known as Ubiquitin-activating enzymes, an enzyme which catalyzes the first step in the ubiquitination reaction, which targets a protein for degradation via a proteasome]
 * E1 regulatory sequence for the insulin gene
 * Estrone, a hormone
 * Pyruvate dehydrogenase (E1), the first component enzyme of pyruvate dehydrogenase complex
 * Acireductone synthase, an enzyme
 * Haplogroup E1 (Y-DNA), a human Y-chromosome DNA haplogroup

Mathematics

 * Exponential integral, $E_1(z)= \int_1^\infty \frac{e^{-tz}}{t}\, {\rm d}t~$, mathematical function
 * the E1 series (number series) of preferred numbers

Medicine

 * E1-isoprostane, a type of isoprostane

Businesses and organizations

 * E1 Music, an independent record label in the United States
 * E1 Corp., a Korean chemical and oil company, member of the LS Group
 * Entertainment One, an international media company

Electronics

 * Honda E1, a predecessor of the ASIMO humanoid robot
 * Olympus E-1, a digital single-lens reflex camera

Places

 * E1 (Jerusalem), an area east of Jerusalem in the West Bank
 * E1 postcode district, London, England, United Kingdom

Other uses

 * E01, ECO code for the closed variation of the Catalan Opening in chess
 * E01, the Encase Image File Format
 * E-1 (rank), the pay grade for enlisted ranks of Private, Airman Basic, and Seaman Recruit in the United States Military
 * E1 grade, a difficulty level in rock climbing
 * E-1 (rocket engine), a liquid propellant rocket engine
 * E1 carrier, an E-carrier European telecommunications standard
 * E1, an AMD CPU from the Bobcat (microarchitecture) family
 * E1, abbreviation for the Oracle JD Edwards EnterpriseOne software
 * E1 on Gardiner's sign list, representing the bull