'''Enjin jet''' merupakan sebuah [[enjin tindak balas]] yang membebaskan [[bendalir]] [[jet (bendalir)|jet]] yang bergerak laju bagi menghasilkan tujahan berdasarkan [[Peraturan pergerakkan Newton|peraturan gerakan]] [[Isaac Newton|Newton]]. Definasi luas ini termasuk [[turbin jet]], [[turbin kipas]], [[enjin roket|roket]], [[ramjet]], [[enjin denyutan jet|denyutan jet]] dan [[pam-jet]]. Secara umumnya, kebanyakkan enjin jet adalah sebuah [[enjin pembakaran dalam]]<ref>[http://www.britannica.com/EBchecked/topic/290504/internal-combustion-engine Encyclopedia Britannica: Internal Combustion Engine]</ref> tetapi bentuk bukan pembakaran juga wujud.
In some common usage, the term 'jet engine' generally refers to an [[internal combustion engine|internal combustion]] [[wiktionary:duct engine|duct engine]], which typically consists of an engine with a rotary (rotating) air compressor powered by a [[turbine]] ("[[Brayton cycle]]"), with the leftover power providing thrust via a [[propelling nozzle]]. These types of jet engines are primarily used by [[jet aircraft]] for long distance travel. The early jet aircraft used [[turbojet]] engines which were relatively inefficient for subsonic flight. Modern subsonic jet aircraft usually use [[Turbofan#High-bypass_turbofan_engines|high-bypass turbofan engines]] which help give high speeds as well as, over long distances, giving better fuel efficiency than many other forms of transport.
About 7.2% of the oil used in 2004 was ultimately consumed by jet engines.<ref>[http://www.after-oil.co.uk/runways.htm How many air-miles are left in the world’s fuel tank?]</ref> In 2007, the cost of jet fuel, while highly variable from one airline to another, averaged 26.5% of total operating costs, making it the single largest operating expense for most airlines.<ref>[http://www.airlines.org/NR/rdonlyres/73AADEC2-D5A2-4169-B590-1EE83A747CDA/0/Airlines_Fuel.pdf U.S. Airlines: Operating in an Era of High Jet Fuel Prices]</ref>