E1, E01, E.I or E-1 may refer to: Transportation 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, a 2012 Chinese electric city car concept E1, a Mazda E type piston engine 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 Science and mathematics 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